Added support for Pushbullet API v2. Dependencies: requests >= v2.0

Notifications work. Needs requests to work. On Debian and Debian- derivates you can install the package python-requests. It needs to be v2.0 or newer, so if you are on Debian Wheezy, you need the version from wheezy-backports.

It uses a slightly modified version of this library: https://github.com/randomchars/pushbullet.py. The modifications are the removal of the listener and file upload to avoid having dependencies on websocket and magic.