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. Updated travis Ruby version to 2.1.1.

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?