Updated Rails to 3.2.18.

Gems `metric_fu` and `capybara` now depend on Launchy.

RSpec: 25 examples, 0 failures
Script: 0 tests: 0 failures, 0 errors, 0 pending, 0 omitted
RuboCop: 11 files inspected, no offenses detected
RuboCop global overrides in `.rubocop.yml`: 2