Updated Gemspec for Capybara 2.1
unlocked capybara-webkit gem to enable the capybara update
Since capybara no longer has the wait_until method, I extracted the functional 
part that mater (the timeout function) to evergreen.
Merge pull request #67 from victormartins/upgrade_to_capybara_2_1

Upgrade capybara  to 2 1