Migrate IDs to int64 type (google#816)

A helper function "Int64" is also implemented to assist the migration of
unit tests.

Refer google#597.

Merge NestedTeamsPreview branch to master (google#747)

* Add support for fetching parent team (for nested teams). (google#723)

Create mediaTypeNestedTeamsPreview const for
https://developer.github.com/changes/2017-08-30-preview-nested-teams/.

Add parent field to the Team struct.

Set preview API media type in endpoints that return a team, so that
the new parent field gets populated.

Helps google#714.

* Add NewTeam struct. (google#724)

This replaces Team with NewTeam in function that accept a team for
creating or editing a team. The NewTeam struct is similar to the
existing NewPullRequest for creating pull requests.

We need a new struct because the set of parameters for creating or
editing a team contains some parameters that are not in the parameter
for teams, and most properties of teams cannot be used for editing.

The specific change is that Teams are returned with a parent field,
but are created/edited with a parent_id field.

Helps google#714.

* Add NestedTeamsPreview header to remaining endpoints

Fixes google#714.

* Change ParentTeamID field to int (from string). (google#748)

Using the code as written in the `NestedTeamsPreview` branch produces
an error when talking to the GitHub API:

	panic: PATCH https://api.github.com/teams/2514825: 422 Invalid request.

	For 'properties/parent_team_id', "2514824" is not a number or null. []

The documentation at https://developer.github.com/v3/orgs/teams/#create-team
states that this parameter is an id type which appears to mean an integer, not a string.
Also, id is an integer in the sample responses for Get team endpoint, etc.

* Bump libraryVersion

* NestedTeamsPreview: Add the ListChildTeams endpoint (google#758)

Remove ListOptions from RepositoryListAllOptions. (google#751)

The standard pagination options have no effect in the /repositories endpoint,
both empirically and according to the documentation:

> Note: Pagination is powered exclusively by the since parameter. Use the
> Link header to get the URL for the next page of repositories.

GitHub API docs: https://developer.github.com/v3/repos/#list-all-public-repositories

Bump up libraryVersion since this is a breaking API change.

Change ListPendingOrgInvitations method to take string org name. (goo…

…gle#731)

The /orgs/:org GitHub API endpoint expects the string name of the
organization, not its integer ID (that would be /organizations/:id
endpoint, which we're generally not using).

Change the org parameter type from int to string to make it possible to
specify the organization via its name.

This method wasn't functional before.

Fixes google#730.

Rename UpdateAt to UpdatedAt; fix JSON tag in Deployment structs. (go…

…ogle#709)

Authorization struct had a "updated_at" JSON key mapped to UpdateAt,
which was an oversight/typo. It has been renamed to UpdatedAt, like all
other similar fields.

Deployments and DeploymentStatus structs had incorrectly mapped their
UpdatedAt field to a non-existing "pushed_at" JSON key. That means
their values were never populated. This change fixes that.

Bump library version as this is a breaking change.

Helps google#605.

Add ListCollaboratorsOptions.Affiliation to ListCollaborators. (googl…

…e#706)

This change adds Affiliation parameter support to ListCollaborators
method by changing its ListOptions argument to a newly created
ListCollaboratorsOptions struct.

This is a neccessary breaking API change. The compiler will help catch
it, and updating code is easy. If the ListOptions argument was nil
before, it can stay nil after. Otherwise, you should change this:

	opt := &github.ListOptions{Page: 2}

To this:

	opt := &github.ListCollaboratorsOptions{
		ListOptions: github.ListOptions{Page: 2},
	}

GitHub API docs: https://developer.github.com/v3/repos/collaborators/#list-collaborators.

Fixes google#647.

Add preview support for Team Review Requests API. (google#682)

This is a breaking API change to support an upcoming github.com REST API
breaking change. It adds support to add, delete, and fetch team review requests.

GitHub Announcement: https://developer.github.com/changes/2017-07-26-team-review-request-thor-preview/

Increase libraryVersion by one.

Fixes google#678.

Rename GitHub Apps installation and installation_repositories events.

With the release of GitHub Apps (was GitHub Integrations), GitHub
have renamed the integration_installation and integration_installation_repositories
event to installation and installation_repositories respectively.

This is a breaking change for those using this API, and can be fixed with:

gofmt -w -r 'IntegrationInstallationEvent -> InstallationEvent' [path ...]
gofmt -w -r 'IntegrationInstallationRepositoriesEvent -> InstallationRepositoriesEvent' [path ...]

Closes google#627.
Updates google#434.

Add *ListOptions parameter to 7 methods that support pagination. (goo…

…gle#635)

This is an unavoidable breaking API change. To update to new version
without changing behavior, you can provide nil value for *ListOptions.

Bump libraryVersion to 7.

This adds a *ListOptions parameter to 7 methods that support pagination,
but inadvertently omitted this parameter:

-	AuthorizationsService.ListGrants
-	GistsService.ListCommits
-	PullRequestsService.ListReviewers
-	PullRequestsService.ListReviews
-	PullRequestsService.ListReviewComments
-	RepositoriesService.ListPagesBuilds
-	UsersService.ListInvitations

This is needed to support pagination. Without this parameter, it’s not
possible to fetch anything other than the first page (of default size)
of results.

Add _withOptions tests for each of the methods, that ignore the result
but ensure that ?page=2 is added to the API requests.

Bump libraryVersion to 6.

There were breaking API changes in previous commit (175a6b4).

Follows google#602.