Added rich text editor instead of markdown

Changed markdowns to rich text editor. 
Installed CKEditor as a rich text editor.

Edit page:
![screenshot from 2014-06-28 16 24 00](https://cloud.githubusercontent.com/assets/5913886/3421827/3b776dda-ff02-11e3-9fb1-f1724daec961.png)

Show page:
![screenshot from 2014-06-28 19 47 18](https://cloud.githubusercontent.com/assets/5913886/3422182/c5559596-ff1f-11e3-9324-e9c68461568a.png)