Access params in enter/exit
* calling apply on a function allows you to pass in the context for `this` which means we can pass in the route into the callback.

[fixes https://github.com/mtrpcic/pathjs/issues/23]
Merge branch '23_access_params_in_enter_exit'
Merge pull request #25 from rmontgomery429/master

Access params in enter/exit
Updated version; fixes issue #23 (after merge of pull from rmongomery429)