Release version 0.2

[mwylde]

This branch contains a major refactoring of the API to split out the BlueZ/linux specific pieces from the generic Bluetooth API. This should allow implementations for other platforms to to re-use the same high level API.

Other additions:

• Support for event handlers for both the central module (peripheral discovery/lost/connection/disconnection) and peripherals (notification/indication events)
• Added support for enabling notify/indicate on characteristics
• Most peripheral methods now have a blocking and async form; this will migrate to futures at some point
• Fixed issues with peripherals that attempt to negotiate a different MTU
• Added docs!
• Lots of other bug fixes