Spree2.0

Commits for changes:

1. Made changes for it to be compatible with spree 2.0.3
2. Change index action in addresses_controller to list down user addresses.
3. Change create action to assign it with current spree user and redirect to addresses index.
4. Change Checkout controller decorator normailze after_filter to use spree_current_user instead of current_user. As, it was giving unexpected behaviour in spree 2.0.

TODO
write rspecs for changes done.