Initial work on noiface work.
Fix a bug surrounding double registering of 0 arity key.
refactoring to use plain functions to do the lookup.
A few todo items.
Some renaming. Start moving abcs into modules.
More renaming and adding abcs to the modules themselves.

Dumped untested cached lookup.
Move IMatcher.
Move LookupError (renamed from ComponentLookupError).
Move PredicateRegistryError.
Export PredicateRegistryError.
Integrate implicit docstrings into implicit module.
Remove an exception that wasn't used, and move NoImplicitLookupError
into implicit.
Also export NoImplicitLookupError.
remove interfaces module. not used anymore.
sentinel refactor.
Rename CachedClassLookup to CachingClassLookup to better describe
what it does.
Some more api documentation, with some more renaming of arguments.
Document dispatch a little, and separate out literal pep443 support
from expanded version.
Rename test to get rid of the leading 0.
compose coverage.