Merge pull request slack-go#999 from toshok/message-timestamp-is-string

link_shared `message_ts` field isn't always a number

Merge pull request slack-go#966 from crisp-dev/new_events

Added more Slack events

-a

Merge pull request slack-go#951 from JustinJudd/patch-1

Use GET /audit/v1/logs instead of POST

Merge pull request slack-go#938 from lch88/fix-missing-token-when-fil…

…e-upload

Add missing token values when uploading a file

Merge pull request slack-go#923 from im-kulikov/socketmode-pass-context

[socketmode] Add methods with passing context

Merge pull request slack-go#921 from kozl/master

Fix authorization on methods which uses get requests