Use Ruby 2.1.2

Hoping this will speed up data-anonymization.
Merge pull request #247 from alphagov/feature/newer-rubbies

Use Ruby 2.1.2
Don’t install development gems in CI

debugger doesn’t work under 2.1.2 and isn’t needed.
Update whenever and chronic

http://stackoverflow.com/questions/14880347/whenever-gem-is-throwing-cant-iterate-from-time-error