Rails 4.1

Rebased master and branched off of payments for this update.

Updated to Rails 4.1 to use AR Enums and Spring.

Added user status to users: registered or active
* Users are registered by default
* Users are active once they have paid the year's dues

Added Spring to development and test environments. Same with Rspec. Replaced mock with double to fix deprecation warnings.

I think the best thing to do here is wait until payments are done and then rebase that to this PR and finally merge into master. What do you think, @stijlist?