Require the poltergeist driver for Capybara

Without requiring 'capybara/poltergeist' I was getting this error:

Error communicating with browser process: no driver called :poltergeist was found, available drivers: :rack_test, :selenium
Edit
Merge branch '1337807-patch-1'
Swap Gemfile-rails4 for Gemfile-rails3
Update rspec-rails
Merge remote-tracking branch 'upstream/master' into origin/master

Conflicts:
	Gemfile