Add new cask for FontExplorer X Pro
user
```ruby
class FontexplorerXPro < Cask
  url 'http://fex.linotype.com/download/mac/FontExplorerXPro402.dmg'
  homepage 'http://www.fontexplorerx.com/'
  version '4.0.2'
  sha1 'de0e20d478ab4321212953cb851e784dbdd20904'
  link 'FontExplorer X Pro.app'
end
```
assistant