Add cask for HipChat for Mac beta
user
```ruby
class HipChat < Cask
  url 'http://downloads.hipchat.com.s3.amazonaws.com/mac-beta/HipChat-0.30-01uennzomg01wmg.zip'
  homepage 'https://www.hipchat.com/'
  version '0.30'
  sha1 'df00f998e1b534d2ff6f1e9e36419bb5c2a4f2c6'
end
```
assistant