Let PullRequest.merge raise an exception if not mergeable
Add tests for GitBlob
Try to rationalize test resources
Todo
Try to rationalize test resources
Try to rationalize test resources
Fix logging
Try to rationalize test resources
Be stricter about API definition

- more warnnings
- reason for deprecated attributes and unimplemented parameters
Fix tests
Refer to structures with doted notation
Remove Entity
Remove GitObject
Remove inheritance between Issue and PullRequest (#265)
Remove inheritance between User and AuthenticatedUser
Fix code generator
Remove most inheritances

This was really difficult to understand and maintain:
- some methods were hidden (mostly in AuthenticatedUser)
- some methods were kept but used a different url (Issue and PullRequest.get_labels #265)
- GitHub may introduce new behavior that breaks inheritance
Restore test coverage for User, Organization and AuthenticatedUser
Restore test coverage for Issue
Restore test coverage for PullRequest + add test for Issue.create_pull