fix typo in comment on UrlMatcher
Delete rule that embarrassingly refers to nonexistent limiter

Limiter existed long ago, but deleted it because
I wasn't using it, had no plans to, and frankly
it didn't seem all that useful. (If you're going
to throttle by IP, you're going to have a large
enough ruleset to write a custom limiter to 
perform the lookup efficiently).
Add Ruby 2.1.3 to travis