Properly support use from Meteor packages

- Applied Tim Heckel's packaging trick

- Better comments

closes #420 and closes #419

meteor-post.js

@@ -0,0 +1,2 @@
+// s will be picked up by Meteor and exported
+s = module.exports;

meteor-pre.js

@@ -0,0 +1,6 @@
+// Defining this will trick dist/underscore.string.js into putting its exports into module.exports
+// Credit to Tim Heckel for this trick - see https://github.com/TimHeckel/meteor-underscore-string
+module = {};
+
+// This also needed, otherwise above doesn't work???
+exports = {};

package.js

@@ -8,7 +8,9 @@ Package.describe({
   documentation: 'README.markdown'
 });
 
+
 Package.onUse(function (api) {
   api.versionsFrom('METEOR@1.0');
-  api.addFiles('dist/underscore.string.js');
+  api.addFiles(['meteor-pre.js','dist/underscore.string.js','meteor-post.js']);
+  api.export("s");
 });