Pass context, event name and data to command constructors

To allow for simple commands w/o execute methods I think it would be a good idea to pass the context, eventName and eventData to the command constructors.

~~I added a spec, but can't get the tests to run (and don't have the time right now to check what's wrong), when I run `npm test` I get an error:~~

~~>Testing: specs/index.html
Warning: PhantomJS timed out, possibly due to a missing Mocha run() call. Use --force to continue.~~