Update adapter.js to enable strict mode without errors.

Extra tweaks, e.g. adding `window.` where appropriate.
Fixed position of DOCTYPE declaration and closing body tag
Moved script elements to end of doc
Added charset and description meta tags
Removed slashes from meta and link elements -- now normal style for empty (void) HTML elements
Tweaks to code formatting and added closing video tags (video is not an empty element)
Removed redundant muted attribute values and removed redundant space at end of link tag
Merge pull request #83 from GoogleChrome/apprtc-index.html-updates

Apprtc index.html updates