Finish refactoring response and input parsers

Feeling better about this. Some failing tests that need some investigation
as far as what the correct format of these messages are, but this is already
a lot better. Now, if I could expand the tests to ensure that we use this
and then interpolate the actual <__nick__> and <__channel__> strings, we
should be golden.
Break out some private methods on GLGInputParser

There could be a model class per request that knows how to create these
requests (and maybe deserialize them) that would further simplify and
reduce the LOC of this class.