Add test and documentation for ``recurse_effects``.
Add some tests from old CallbackTests.
Get rid of unused POPOIntent.
Add docstring to test_dispatcher.
Some more twisted tests.
Get rid of legacy_dispatcher.

rackerlabs/otter#857 removes the only extant user.
Fix lint.
Merge pull request #18 from tomprince/better-intent-dispatching-2

Address some review comments.