Merge pull request #10 from tomprince/better-intent-dispatching-2

Continute implementing better-intent-dispatching on top of better-intent-dispatching-2.
Merge remote-tracking branch 'remotes/tomprince/better-intent-dispatching-2' into better-intent-dispatching-2
fix effect.test_base.EffectPerformTests.test_error_with_callback
a bit of a glossary in the __init__ docstring
minor docstring fix in perform
Add some test docstrings.