Requiring headless.
Changing example url.
Merge remote-tracking branch 'upstream/master' into new_headless
Merge remote-tracking branch 'upstream/master' into new_headless
Adds headless option for page's js content.

- Option recrawls a page given proper http responses.
- rspec integration test must have the spec/headless_test_endpoint.rb up
  and running on port 80 for now.  Use rvmusdo ruby
headless_test_endpoint.rb for now.
Fixes global tests.

- bundle exec rake works now, needed to handle fakeweb's web mode.
Speeding up headless_wait in tests.
Merge pull request #18 from DavidLGoldberg/new_headless

option to use selenium headless being merged.  w00t