Remove unnecessary dependency from Rakefile

Also minor tidy in gemspec.
Add feature tests for vCloud Query

And dependencies to gemspec.
Add rake task for Cucumber feature tests
Include feature tests in default Rake task

Also, move default to top so it's not lost, and update README for new tests and default task.
Add t.fork = false

This apparently leads to faster startup: http://rubydoc.info/github/cucumber/cucumber/Cucumber/Rake/Task, http://aaron-jensen.com/post/5019042852/speed-up-your-rspec-cucumber-run
Merge pull request #18 from alphagov/add-feature

[#67235848] Add vCloud Query feature tests to vCloud Core