Add EasyTAG 2.1.8-mac-alpha-1 This is not an official build.
user
```ruby
class Easytag < Cask
  url 'https://github.com/rfw/easytag-mac/releases/download/v2.1.8-mac-alpha-1/easytag-v2.1.8-mac-alpha-1.dmg'
  homepage 'http://rfw.name/easytag-mac/'
  version '2.1.8-mac-alpha-1'
  sha256 'e637033759396911ed3988fd9349657a6db151821fb21759560ffa220fa3a877'
  link 'EasyTAG.app'
end
```
assistant