IA Pages - add cancel button for edit mode

@russellholt Clicking on the cancel button will redraw the section with the proper pre-edit template without saving the changes.

[Screencast](http://gfycat.com/SilentPleasantDwarfrabbit#?speed=2)

Screenshot:
![screen shot 2014-11-03 at 16 07 02](https://cloud.githubusercontent.com/assets/3652195/5089882/619960a2-6f3e-11e4-8b52-b82ec3fa3dbf.png)