Make the javascript module API nodey.

Add a createScript function, and put stuff on exports instead of hiding
it in exports.Script.

lib/javascript.js

@@ -1,3 +1,11 @@
 var binding = process.binding('evals');
 
 exports.Script = binding.Script;
+exports.createScript = function (code, ctx, name) {
+  return new exports.Script(code, ctx, name);
+};
+
+exports.createContext = binding.Script.createContext;
+exports.runInContext = binding.Script.runInContext;
+exports.runInThisContext = binding.Script.runInThisContext;
+exports.runInNewContext = binding.Script.runInNewContext;