Upgrade to Ruby 2.1.1 and Rails 4.0.3

While this is running on the latest Ruby/Rails, it includes some gems
that provide backwards compatibility for Rails 3.x. Further work is
required to be completely migrated to 4.x. Some gems are still behind as
well, and will need more work than a simple upgrade (e.g. bootstrap).
Use dotenv gem for development and test
Add Heroku integration gem for production/staging
Load city image via asset pipeline
Use binding_of_caller gem in development

This provides REPL support in development when a 500 error occurs.
Move to strong_parameters
Merge branch 'rails4'
Add Travis config
Merge branch 'travis'
Update schema.rb with Rails 4 conventions

Mostly just converts `:key => value` to `key: value`, but also includes
some comment changes.
Update shoulda-matchers
Remove competition start date validation

This is really getting in the way of creating data for tests, and it
doesn't currently server any purpose, since there's no functionality to
create a competition via the app.
Track intermediate scores on memberships

Adds a ride_count column to the memberships table, which keeps track of
a user's contribution to a team. Changes the score calculation process
to utilize the intermediate values.
Add script to update ride counts
Merge branch 'score-performance'
Merge branch 'master' into production