Why:
* The `route` matcher can not only be used within controller example
groups but also routing example groups.
* Now that we are mixing matchers into specific example groups, `route`
is no longer available in routing example groups.
To satisfy the above:
* Create a new module that contains a `route` method and returns a new
instance of RouteMatcher. (RouteMatcher still lives in the
ActionController namespace.)
* Mix this module into routing example groups when the gem configuration
block is run.
