Introduce formal generators.

Introduce a shallow hierarchy of simple generator classes, collecting
common functionality and allowing for future snap-in generator
replacement. Use John Resig's "class"-based inheritance per
http://ejohn.org/blog/simple-javascript-inheritance/.

src/gen/base-generator.js

@@ -0,0 +1,13 @@
+/**
+Base resume generator for FluentCV.
+@license Copyright (c) 2015 by James M. Devlin. All rights reserved.
+*/
+
+(function() {
+  var Class = require( './class' );
+  var BaseGenerator = module.exports = Class.extend({
+    init: function( outputFormat ) {
+      this.format = outputFormat;
+    }
+  });
+}());