title: i18n language files. How to manage missing and unused keys
body: <p>I have a Rails/Angular webapp. We use two different methods to translate our app: <a href="https://github.com/globalize/globalize" rel="nofollow">Ruby Globalize</a> i18n with the corresponding yml language files, and <a href="https://github.com/angular-translate/angular-translate" rel="nofollow">angular-translate</a> with the corresponding json language files. Managing language files can be a pain. I just found the <a href="https://github.com/glebm/i18n-tasks" rel="nofollow">i18n-tasks gem on github</a> to help find missing and unused keys in my yml language files. It works great! Does anyone know of a similar static analysis tool to help manage json language files? Is there a better way to do this?</p>
  
  <p>As I write this I am wondering if there is some sort of i18n transpilation that I could do. Keep a single language file and generate the yml and json from that. </p>
  
  <p>Features wanted:</p>
  
  <ul>
  <li>sort keys alphabetically</li>
  <li>delete unused keys in all language files</li>
  <li>add missing keys in all language files</li>
  </ul>