Merge pull request #50 from ryansch/capybara-2.1

Capybara 2.1
Bump capybara to 2.1 explicitly because of backward incompatiblity.

Addresses #51.
Require mechanize 2.7.0 or newer
Comment out focus in spec_helper.
Merge pull request #53 from ryansch/capybara-2.1

Capybara 2.1