Respecting new Spree localization practices + resolving issue #28

Resubmitting.

"Product.method(self.name.intern).arity == 0" will not work for "ascend_by_updated_at" and other sorts cause it returns -1. This is because such scopes (added as simple scopes) were added via "scope" method, not like other scopes that were defined via "define_method". So this request should fix #28.

I saw a lot of "t()" helper was used in partials. This request also updated all views with "Spree.t" helper using. It adds correct translations too.