fixes easy drop down at checkout

This pull addresses a number of issues resulting from the use of the easy drop down menu with the state selection menu at checkout.

Inconsistancy with respect to menu sizing and selection return value have been fixed by upgrading to the current version of easy pull down.

The incorrect display of the state selection box for countries without states and the inability to dynamically update state selection options are fixed by overriding the fillStates function which is originally part of checkout.js of the Spree frontend.  In order to use the new function I had to unbind previously set change event handlers and rebind them to a redefined updateState function which references the new fillStates function.

-Jesse