Rename an unfortunately-named function.

In conf.py, the "set" function shadowed the built-in "set" type.  That was an
unfortunate choice of name, but fixed easily enough.
Switch RegexMatcher to use .search() instead of .match()

This ensures we can use RegexMatchers to match on substrings as well as entire strings.
Rename input.py to catinput.py .
Add TODO to documentation of ProtocolMatcher.

A note that ProtocolMatcher should be refactored.
Resolve AndCombinedMatcher bug.

This bug caused AntCombinedMatcher.matches() to return None instead of True.
Add unit tests for matchers.
Add unit tests for CatInput.
Update TODO