Add 'play' method to allow for playing of sounds.

There is no ability to send sounds to Campfire directly from the
response message object. However, using Campfire you simply "/play
sound".

Add this ability to the `Adapter` and the provided default adapter
implementations. It is added to the `Shell` adapter to allow for an
easier time at testing / debugging scripts using the local shell.

Add to the `Campfire` adapter as this is the core place where it
can be used.
Add default play implementation on Adapter.

This will log a warning if the loaded adapter does not implement the
`play` function and a script calls it.
Merge branch 'campfire-play-patch' of https://github.com/cupakromer/hubot into cupakromer-campfire-play-patch
Update tomdoc formatting
Remove warning and shell play function