Merge pull request #1 from bbeeley/master

Prevent adding watchers after hangup.
Removed Mouse, Updated Documentation.

Removed the dependency on Mouse.  This will need to be pushed along with
AnyEvent::Blackboard being updated which hasn't been done yet.

Reordered the methods so they appear in a more natural fashion in the
documentation, and update the documentation to have a better description of the
component.

Created a new accessor ``hungup'' which describes, as one might hopefully
guess, whether or not hangup has been called.  Made the tests depend on this,
rather than the private value ``_hangup'' which is now gone.  This also means
that was the only real API encapsulation violation in the unit tests.
Release 0.3.8
Fixed release, 0.3.9.

The merge of the last two changes didn't go so cleanly, turns out that
the change which removes Mouse kills the accessor ``_hangup''.  This
changeset will require a release to ``AnyEvent::Blackboard`` as well.
Fix check for hungup in _watch