enable optional controller and templates for modal (#29)

[selvach]

Some quick changes to allow:

• passing in a custom template with options.template
• passing in a controller name with options.controller
• added deferred to modalScope to allow custom controller to close the modal and resolve / reject the promise

Probably better ways to do this. Also need to solve passing in data, components and other options.

[IdanCo]

Awesome! looks like an excellent solution!

Do you mind adding an example in the docs? It doesn't have to include complete documentation, simply some example so i could test it.