Refactor start_with and end_with matchers.

- Leverage instance variable state.
- Leverage the description/failure messages
  provided by BaseMatcher.
- Remove ternaries.
Rename spec file.
Refactor to use the new FuzzyMatcher from rspec-support.
Make `change` composable with other matchers.
Make `include` matcher fully composable.
Make `raise_error` matcher fully composable.
Make `match_array` fully composable.
Make `start_with` and `end_with` fully composable.