Add FireFox Beta for Japanese
user
```ruby
class FirefoxBetaJa < Cask
  url 'https://download.mozilla.org/?product=firefox-31.0b1&os=osx&lang=ja-JP-mac'
  homepage 'http://www.mozilla.org/ja/firefox/channel/#beta'
  version '31.0b1'
  sha256 '7847e1aa50394d84bbe62cb5a9e61dc1f8671da301c174e517afb7049da50177'
  link 'Firefox.app'
end
```
assistant