Add support for Adhearsion

Looking forward to helping document Adhearsion! :-)

Much of what would be needed to "support Adhearsion" is already in Dexy, but a few upcoming features such as:

• custom YARD template to better support Ruby gems
• support for Chef and/or Puppet configuration

will contribute to this.

Probably the most important (and interesting) challenge here is to find an equivalent of 'screenshots' for telephony apps. Ideally, we'd like to find a way to record the audio of an interaction, so that this recording can be shown next to the code that generated it.