title: Yeoman composeWith only calling constructor in subgenerator
body: <p>I'm trying to use <code>composeWith</code>, to call a subgenerator within the same generator package. Yet for some reason, only the constructor of the called generator is invoked.</p>
  
  <p>My generator-package <code>generator-test</code> looks like this:</p>
  
  <pre><code>package.json
  generators
  -- app
    -- index.js
  -- base
    -- index.js
  </code></pre>
  
  <p>My main generator in <code>app</code> looks like this:</p>
  
  <pre><code>'use strict';
  
  var yeoman = require('yeoman-generator');
  var yosay = require('yosay');
  
  module.exports = yeoman.generators.Base.extend({
      constructor: function () {
          console.log('constructing app');
          yeoman.generators.Base.apply(this, arguments);
      },
      initializing: function() {
          console.log('initializing app');
          var done = this.async();
          this.composeWith('test:base',{ options: { } })
              .on('end', function() {
                  done();
              });
      }
  });
  </code></pre>
  
  <p>My subgenerator in <code>base</code>:</p>
  
  <pre><code>'use strict';
  var yeoman = require('yeoman-generator');
  
  module.exports = yeoman.generators.Base.extend({
      constructor: function () {
          console.log('constructed base');
          yeoman.generators.Base.apply(this, arguments);
      },
      initializing: function() {
          console.log('initialized base');
      }
  });
  </code></pre>
  
  <p>This should generate 4 console outputs, yet I am only getting the first three:</p>
  
  <pre><code>constructing app
  initializing app
  constructed base
  </code></pre>
  
  <p><code>initialized base</code> is never displayed. Why? Am I misunderstanding the concept of <code>composeWith</code>?</p>
  
  <p>Or is there another way to solve this?</p>