More tests.
Whoops! Now making sure to call the parent router
constructor...
Updating the signature of `handleRouteCallback()`
Fixing some old tests to work with new Klein
behavior
Merge pull request #9 from Rican7/bugfix/invalid-router-construction

Bugfix - Invalid router construction
Strictly check if data is null instead of empty in order to return what's expected
Adding a test :)