Additional improvement to CommonJS Modules support

Now implements (and mostly follows) requirements of Modules/1.1 spec
  implementes only the required "secure sandbox" subset of the spec
  `module` free variable changed from the `moduleInfo` to an id container
  `require` free variable given a "main" property
  boot module scope closed and exported
    this also changes the interface between boot and bootprefix slightly
    (should now be able to create multiple TW instances under node)
 BREAKING CHANGES:
  The tiddlywiki module itself now exports a single constructor function
  Modules which depended on `module` referring to `moduleInfo` will break
  Modules which don't conform to Modules/1.1 will break
    (by attempting to modify require.main or module.id)

boot/bootprefix.js

@@ -12,12 +12,11 @@ See Boot.js for further details of the boot process.
 
 \*/
 
-// Set up $tw global for the browser
-if(typeof(window) === "undefined") {
-	global.$tw = global.$tw || {}; // No `browser` member for the server
-} else {
-	window.$tw = window.$tw || {browser: {}};
-}
+var _bootprefix = (function($tw) {
+
+"use strict";
+
+$tw = $tw || {browser: typeof(window) !== "undefined" ? {} : null};
 
 /*
 Information about each module is kept in an object with these members:
@@ -81,3 +80,18 @@ Convenience function for pushing a tiddler onto the preloading array
 $tw.preloadTiddler = function(fields) {
 	$tw.preloadTiddlers.push(fields);
 };
+
+return $tw
+
+});
+
+if(typeof(exports) === "undefined") {
+	// Set up $tw global for the browser
+	window.$tw = _bootprefix();
+} else {
+	// Export functionality as a module
+	exports.bootprefix = _bootprefix;
+}
+
+
+