Adding Markdown option for project/step text

[darylr]

Add option to set default editor on your profile (tiny_mce or markdown) and ability to change type for existing projects. Could be lowered if editor type can't be changed after project creation, or alternatively, if we could use jquery-markedit

[vkurup]

Some comments, so I don't forget once we do get around to implementing:

Julia: "For the PyCon 2014 site, we are using http://tstone.github.io/jquery-markedit/ It is pretty straightforward + allows you to have a live preview of your work"

daaray: "Most of the important bits are in this app in the pycon repo:
https://github.com/caktus/pycon/tree/develop/markedit
The code is repurposed/updated from: https://github.com/tstone/jquery-markedit/."