Handling empty comments.

GitHub rejects empty comments. These mostly come from a GoogleCode
change (like marking an issue as fixed), and providing no comment.
We could probably do a better job of mapping these to a more useful
comment (or tag).
Allowing comments in user mappings file.
Creating new GitHub issue with proper description.
Closing issue *after* adding all comments.

Adding comments to an already closed issue is confusing and doesn't match
the timeline on code.google.com.
Fixing up comments for GitHub.

GitHub interprets all comments as Markdown. However, since our comments
originate in a different system (not Markdown) we must first fix them up
to avoid some incorrect interpretations by GitHub.

This function will:

1. Preformat part of comment if it detects part of the comment that
   it deems necessary to preformat. Once begun the rest of the comment
   is preformatted.

2. Disable the #n Git reference linking. These mostly appear when a
   code stack is pasted into a comment, which causes an incorrect
   reference to an unrelated issue.
Saving project name for use when linking.
Adding metadata to comments to link back to Google Code.

Because the GitHub REST API doesn't allow the specification of login
(i.e author) or time we need to modify the comments to maintain the
issue's provenance.
Sleeping in between comment uploads.
Supporting repository names with embedded login or org.

Don't assume that the repository is owned by the user.