Improve hash formatting used in `include` matcher.

{:a => 1, :b => 2}

...reads much better than:

{:a=>1, :b=>2}
Rename spec file.
Refactor to use the new FuzzyMatcher from rspec-support.
Make `change` composable with other matchers.
Make `include` matcher fully composable.
WIP: raise_error composability