Reformat/update docstrings
Rename method_framing to method_io

This module is responsible for reading and writing AMQP methods, not framing
them. Framing is now done in proto.py.
Rename AbstractTransport -> Transport
Document x-max-length argument
Set content_encoding automatically if str

* Docstrings have been reformatted.
* ack() now raises an Exception if attempting to ack a message with no delivery
  tag.
Modify Sphinx styles
Change colour
Add shell prompt prefix to example
Add DejaVu Sans Mono woff files
Bump version