Setup for Selenium tests

RVM (.rvmrc) makes sure the correct version of Ruby is used and that
all Ruby gems are installed into a sandbox (or gemset).
Bundler (Gemfile and Gemfile.lock) makes sure all required Ruby gems
(and versions of gems) are installed.
Rake (Rakefile) makes it explicit how to run the tests.
Cucumber (cucumber.yml, env.rb, sauce.rb) is the test runner.
config.yml holds almost all configuration (usernames, supported
browsers...)

Change-Id: Iea9213fa732fecd7dfde85e00d513dd332a4061a