fix (delimitedProtocol): add check for transport

Add check for this.transport before attempting to write it. This could
be done at the base protocol layer but this approach matches the
other methods in the base protocol check for this.transport instead
of ensuring it exists.
Merge pull request #67 from gameclosure/fix-delimited-protocol-with-no-transport

fix (delimitedProtocol): add check for transport
Remove extra whitespace in PubSub
Add tests suite; add PubSub listener inversion

lib.PubSub now has two additional methods inspired by the Backbone
events API - `#listenTo` and `#stopListening`. All listeners created
by `listenTo` will be removed all at once when `stopListening` is
called. Being able to remove all the listeners in this fashion makes
listener leaks easy to avoid when repeatedly constructing/deconstructing
objects.

There are tests for these new methods in a folder called `tests`. The
method interfaces are documented with JSDoc style comments within
PubSub.js.
Merge pull request #68 from gameclosure/feature-pubsub-listener-inversion

Feature pubsub listener inversion
Merge branch 'develop' into feature-node