Multiple event reaction

This should correct #18 by changing the `respond_to` method to accept a splat of events.

I also had a failing test due to the stub syntax used. I have updated it to work for ruby 2.0.0p195 and rspec 2.14.1.

Thankfully your underlying code was very flexible and so there is really very little changed although I have included a couple of specs to document and demonstrate the new feature.