Add poltergeist to gem file, and limited version dependecies

spec/spec_helper.rb

@@ -1,6 +1,7 @@
 require 'rubygems'
 require 'spork'
 require 'rails'
+require 'capybara/poltergeist'
 #uncomment the following line to use spork with the debugger
 #require 'spork/ext/ruby-debug'
 
@@ -24,6 +25,8 @@ Spork.prefork do
   # in spec/support/ and its subdirectories.
   Dir[Rails.root.join("spec/support/**/*.rb")].each {|f| require f}
 
+  Capybara.javascript_driver = :poltergeist
+
   RSpec.configure do |config|
     # ## Mock Framework
     #