added MIT license

Hi Igor,

This example app is incredibly helpful to me, and I'd very much like to incorporate parts of this in my project. I'm fairly new to Angular, yet this example very much makes sense to me. 

Moreover, it's obviously a good practice to clearly state licensing/copyright terms for open source projects.

I chose the MIT license because it is liberal in its usage terms, but if there is a difference license you prefer, I'd be happy to send a different pull request.

Best,

Alan