consolidate new post form variants into single client-side template/view

@marcotuts @gwprice 

*not yet ready for merge*  views.py still needs some cleaning up.  however, the templates and backbone views are where they need to be to move forward.

Our general pattern for this kind of thing is to put a placeholder div in this template and then have the render function populate it as a separate step. I'm not sure which way I like better, but did you make a conscious choice to break with that pattern, and if so, why?