Adding the Session 04 content for Issue #5
Merge branch 'dev'
Merge branch 'master' of github.com:miguelpdl/WebRTC-codelab into gh-pages
Updating the Index page for the Lab with Session 04 for Issue #5
Merge branch 'dev'
Merge branch 'master' of github.com:miguelpdl/WebRTC-codelab into gh-pages