Feature/markdown toggle

Hi jon, here i've done a few things. main ones are:
-adding uses_markdown cols to the comment, discssion, motion and user tables
-created a conditional_markdown function which renders markdown based on .uses_markdown boolean for object 
-added a button which ajax-sets the user's .uses_markdown preference

NB
-removed bootstrap-sass gem?
-minor formatting (the user privacy box now pops to the right for IE workability)
- a couple of other minor changes i've forgotten about but you've asked thrown in as we've progressed