Fix HTML pages to use layouts

Replacing temporary copies of complete HTML with use of jekyll layouts:

* [x] peer-network-training/08-22-2013
* [x] peer-network-training/07-11-2013-jared
* [x] peer-network-training/07-18-2013
* [x] events/codeacross-2012
* [x] events/codeacross-2013
* [x] supporters