Add Cantonese and traditional Chinese locals

https://www.pivotaltracker.com/story/show/47034803
Add english transaltions for zh-hk zh-tw
Add in local files for zh-tw and zh-hk
Regenerate yaml
Add zh_TW and zh_HK to right-to-left tests
Merge pull request #473 from alphagov/chinese-locales

Add Cantonese and traditional Chinese locals

https://www.pivotaltracker.com/story/show/47034803