Updated instructions for Capybara 2.0
Updated instructions for Capybara 2.0

"Requests" is now "Features" and thus spec_helper.rb needs to be
tweaked slightly.

pgib/twilio-test-toolkit,pgib/twilio-test-toolkit,pgib/twilio-test-toolkit,JMongol/twilio-test-toolkit,JMongol/twilio-test-toolkit