Refactor

Fixes #6 

- Refactor all the code (breaking changes).
  - Support to all methods of the official HipChat API
  - Added the following custom methods:
    - `rooms.getByName`
    - `rooms.getByXmppJid`
    - `users.getByMentionName`
    - `users.getByName`
    - `users.getByEmail`
    - `users.getByStatus`
  - Added tests (finally)
  - Added documentation on docs folder
  - Updated README