Merge pull request #1438 from mollybostic/master_0430

fixing formatting issues, metadata, switcher; no staging required.
fix 2 xhtml bugs
Adding Twilio Mobile Service Tutorial
Merge pull request #1441 from devinrader/master

Added Twilio Mobile Services tutorial
Merge pull request #1440 from RickSaling/join

fix 2 xhtml bugs
fixed validation errors