feat(resumable-media): add customizable timeouts to upload/download methods

[plamut]

Fixes #45.

This PR adds configurable timeouts to upload objects.

Motivation:
We would like to add timeouts to BigQuery methods that depend on the file upload functionality (using resumable media), so that requests do not get stuck indefinitely at the transport layer.

Currently there is a default timeout used (61, 60), but that might not suit all use cases, hence the need for optional explicit timeout parameters.

CAUTION: Changing public function signatures might break some libraries that utilize resumable media, even though the new arguments are optional, and positioned last), and this will not be caught by the test suite.

It has happened recently when we added timeouts to google-auth, thus it is advisable that code owners of the dependent libraries have a look, too (if that is feasible).

[plamut]

Unit tests suite fails under Python 3.4, created an issue (#117). The 3.4 tests pass, though, if ran in isolation.

Update: Will beWas addressed in #118.

[anantzoid]

I've been facing ReadTimeout issues while reading the data from GCS and noticed _DEFAULT_READ_TIMEOUT = 60 cannot be changed by the user for read requests [src].

The user should be able to specify timeout while using download_to_file and similar functions.

[plamut]

@busunkim96 Somehow this slipped out of the focus, and it might be a good time to revive it. Added you as a reviewer based on the GitHub's suggestion, but feel free to delegate to someone else if that makes more sense, thanks!

@anantzoid Thanks for bringing this back to attention. As this PR only adds configurable timeouts to uploads, I can add the same for the download methods, too, provided that the original feature request is confirmed (I personally don't see any reason why it shouldn't be).

[busunkim96]

LGTM'd, but adding @crwilcox since the storage folks are other primary users of this library

[plamut]

I will update the PR with timeouts to the download methods as well.

[plamut]

@crwilcox Friendly ping, can you take a look? Thanks!

[plamut]

@busunkim96 @frankyn Thanks for the reviews!

When would it be possible to release a new version of google-resumable-media in order to unblock googleapis/python-storage#185 ? I hear this week is a holiday period there?

[frankyn]

Hi @plamut, let's wait until next week when everyone is back.

[plamut]

Sounds good, there's no rush.