Add the ability to get the index path with an associated cell action.

This PR adds the `:index_path` data to action attributes so that when you do something on an `:action` you have a way to figure out which cell it was actually performed on.

Uses for this include being able to reload just that cell using `tableView:reloadRowsAtIndexPaths:withRowAnimation:` instead of reloading the entire table. This is really useful for gigantic tables that take a long time to reload.

Includes passing test.
Looks good. Would you mind tightening this up a little by using when x then y?

```ruby
when 0 then self.send(action) # Just call the method
```