Merge pull request #117 from sbesson/75_rcleanup

Check for remote existence in rcleanup
Decorate GithubRepository initialization method with retry decorator
Add unit test class for testing internal retries decorator
Add unit test for no retry GithubException
Refactor repo/user error generation to test other exceptions
Wrap socket timeouts in internal retries decorators.

Fix #48
merge master -D org -I include -E exclude: PR 119 (Add unit tests for internal GH API call retries)