821 embed widget template

This contains the work on the embed widget template to date. Seems mostly ok in Safari, FF, Chrome, and IE8. Generally some more tweaking of breakpoints and layout might be appropriate.

Please review the commit comments and let me know if you have any questions.

One outstanding issue: in IE8, media queries are not working when the widget is in an iframe (they do work when widget URL is loaded directly). Currently using css3-mediaqueries.js because its setup was simpler than respond.js, however respond.js may get this working. If not, the best route might be some simple jQuery-driven dimensions check and CSS class additions.