chore(docs): use GAE and Google CDN for docs

Short summary: if you use local node server everything should work as before,
if you use GAE, everything should work now as well, but we pull assets from CDN.

- GAE doesn't support ':' in filenames, so I had to replace it with '_'
  but only in the filename, all servers were reconfigured to rewrite the
  urls from : to _ when doing file lookup
- We now pull angular assets from google CDN when deployed on GAE (locally
  or in production). When running on a non GAE server we pull assets from
  ../ directory as before
- Since only certain versions of Angular are available on CDN and we want
  to be able to autodeploy docs, I had to pin down the Angular files
  to a "stable" version when running on GAE

lib/nodeserver/server.js

@@ -108,6 +108,10 @@ StaticServlet.prototype.handleRequest = function(req, res) {
       path = path.replace(match[0], '/index.html');
       sys.puts('Rewrite to ' + path);
   }
+
+  // rewrite : to _ to be GAE-friendly
+  path = path.replace(':', '_');
+
   // end of docs rewriting
 
   fs.stat(path, function(err, stat) {