Adds SpreedlyCore Gateway support

Fixes #148
Send invoice number in auth_capture method of Authorize.net CIM getaway

Fixes #147
Use Spree 2.4.0.beta
Use 'name' in Braintree specs
Use name field in pin and usa_epay gateways too
Require sass/rails
Pass billing address to braintree to allow address verification

Fixes #157