Update to Rails 4.1.1

Also includes updates for the other dependencies, and updates to the Travis config to properly setup a Rails 4.1 environment.

I wasn't initially planning on updating to 4.1 for this summer, to avoid any potential issues a "last minute" update can bring. However, I think I'll be using [ActiveRecord Enums](http://api.rubyonrails.org/v4.1.1/classes/ActiveRecord/Enum.html) (introduced in 4.1) to change ride types from `is_round_trip` to be a type field with enums, to account for logging vacations.