Updated path to require.js

Path was `requirejs.js`, but is actually `require.js` in component directory.
Ensure callback is not undefined before trying to access properties
Checking that callback is of type function and that `type` is set before being used in error message
Merge pull request #35 from alex-seville/master

Rearrange undefined callback check in On
put param marshaling together, callback can be object
test wrong callback type throws right exception
precompile 2 regexes
Added ability to trigger custom events with a preventable default behavior.
Merge pull request #42 from kloots/add_default_behaviors

Added ability to trigger custom events with a preventable default behavi...
events can define default functions
Merge branch 'master' of github.com:twitter/flight