title: Jest preprocessor for Typescript/ES6
body: <p>I am trying to test A Typescript Class Using Jest. Since I need to use  es6's <code>async/await</code> I need the typescript class to be compiled to es6 first and then to es5 using babel. What do I need to add to the preprocessor in order to achieve this.
  My current preprocessor looks like this: </p>
  
  <pre><code>const tsc = require('typescript');
  
  module.exports = {
      process: function(src, path) {
          if (path.endsWith('.ts') || path.endsWith('.tsx')) {
              return tsc.transpile(
                  src,
                  {
                      module: tsc.ModuleKind.CommonJS,
                      jsx: tsc.JsxEmit.React
                  },
                  path,
                  []
              );
          }
          return src;
      }
  };
  </code></pre>
  
  <p>Do I need to add <code>target: tsc.ScriptTarget.ES6</code>?
  When I do so I get an <code>unexpected identifier =</code> error in the processed code which looks like the transpiled version of my <code>.ts</code> class. What I gathered from this is that my preprocessor is compiling data to es6 but my es6 is not being transpiled to es5.
  Also is there any readymade preprocessor which can do this? </p>