Fixes New Braintree Cancel Method

Fixes #152
Pass empty previous_cards to gateway partial.

Fixes #153
No more Versionfile
Mention that you need to require another gem for braintree
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
enforce card verification
Fix deprecations.
Update travis.
Change card.type to card.brand to match Stripe API change.
Fixes #170