Remove TODO from gcloud.storage.bucket.

Re-introduced in 2f930652860400831e9fc1f3ef2dbf7179fcce26 after
being removed for #162 as part of the effort in #175.
Updated docstring on Key.rename() with a warning.

I have a pending request to the GCS team asking if this is a reasonable thing to have exposed, however based on our conversations in #99 and #224 it seems that it needs to exist regardless (if we don't provide it, people will just do this on their own).

That said, we need to be clear about what's happening under the hood in the short part of the docstring. If someone is frequently "renaming" 5TB objects (that's the maximum size currently), this could actually change their bill a lot and make the GCS API do some ridiculous amounts of work. For small objects this shouldn't really be a problem.
Revert "Updated docstring on Key.rename() with a warning."

This reverts commit aa2e66a7de78d46aa4b9b7bc02ba6acb84406ae5.

This was meant as a pull-request, not a direct commit.
Updated docstring on Key.rename() with a warning.

I have a pending request to the GCS team asking if this is a reasonable thing to have exposed, however based on our conversations in #99 and #224 it seems that it needs to exist regardless (if we don't provide it, people will just do this on their own).

That said, we need to be clear about what's happening under the hood in the short part of the docstring. If someone is frequently "renaming" 5TB objects (that's the maximum size currently), this could actually change their bill a lot and make the GCS API do some ridiculous amounts of work. For small objects this shouldn't really be a problem.
Merge pull request #236 from jgeewax/master

Updated docstring on Key.rename() with a warning.
Removing gcloud.credential.Credential class.

No instances of this class were ever created and it only had
one factory method, which is now a function. This class was
also misunderstood / misreferenced in the docstring mentions.
Updating docstring on credentials.get_for_service_account function.