Update hooks methods. Add repository status methods.

Problem description
===================

The current txgithub does not provied repositories status methods:

http://developer.github.com/v3/repos/statuses/

Also hooks methods are not complete:
http://developer.github.com/v3/repos/hooks/


Changes description
===================

I have added all statuses and hooks methods described in GitHub docs.

Tried to add some basic tests for the new code. The tests uses a rudimentary mock as I didn't wanted to add an extra dependency.

What do you say about renaming GithubApi to GitHubAPI ? GitHub is the name listed on GitHub website and API is a acronym.

Please let me know what convention to use for the docstrings.


How to try and test the changes
===============================

reviewers @tomprince

trial txgithub.tests


Other comments
=============

The current code does not pass pyflakes checker. Would you like to have a pyflakes compliant code?

The current txgithub API is a bit to rough for my taste. Would like like to implement an API where you don't need to repeat the repo name in all calls and the method will return objects instead of dictionaries?

Ex:
```python

hub = GitHubAPI(token='sdfsaf')
my_repo = hub.repositories.get(owner='bla', repo='tra')
my_repo.getHooks()
hook = my_repo.getHook(1)
hook.delete()
hook.edit()
hook.test()
```