[api] allow understudy to be required directly
Merge pull request #4 from jcrugzz/simpler-require

[api] allow understudy to be required directly
[api] have perform receive last arg callback that is called before execution of after hooks
[test] modify tests for new api and add a test where an after hook errors
[fix] add comment for onFinish arg
[fix] also make sure onFinish is present and a function
[doc] Make variable names less obtuse. Improve comments
[fix] Short circuit before calling nextInterceptor when no interceptors exist
[minor] Remove unused noop function
[dist] Move `lib/index.js` to `index.js`.
[dist] Use proper tags.
[fix] Blow up if either function is not defined.