Spree 2.4

[rbngzlv]

Hi!

This pull request is for create a 2-4-stable branch.

• [x] Update dependencies for require spree 2-4-stable branch
• [x] Update assets structure folder
• [x] Move install generator inside the correct folder (this also fix the dummy app creation)
• [x] Reuse form address from spree_frontend gem
• [x] Fix javascript for fix unbind event (this also fix some test)
• [x] Udate tests to RSpec 3
• [x] All tests working again