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
* [ ] events/codeacross-2012
* [ ] events/codeacross-2013
* [ ] apps/postcode
* [ ] supporters