Add start of Repos/Stats module

This doesn't yet implement all endpoints, but it is a start at least
Make the sleep optional

This commit introduces the optional argument `wait_for_200`, which will cause
contributors to keep trying until it gets a response that is not 202.

Other suggestions for argument name might be:

* auto_wait
* wait_for
* auto_202_sleep

Not sure which one (if any) I actually like.
Merge pull request #152 from omega/repos-stats

Add start of Repos/Stats module