Updated Rivets to 0.4.8; now uses AMD
Added utils function to fire custom events
Updated fireEvent call to use abstracted module
Added event listener to refresh rivets bindings
Added accepting multiple execution args via more form fields

Fixes #39

This isn't as clean as I was hoping.

It works by bypassing the Rivets adapter on the ``arg`` iteration
binding then manually redrawing the list of args only when we're ready
(when the + button is pressed). Redrawing is handled by resyncing the
Rivets binding via a custom event.

This is needed because the default for-each-* binding destroys and
recreates all <input> elements which interrupts you as you're typing in
an input box. A more optimal solution would be to create a version of
for-each-* that reuses existing DOM elements. This will also be useful
down the road when we're dealing with very large collections.