Added useful key-bindings

I added (in my opinion) some useful key-bindings that really help when navigating questions. I would think that you would use these in the first place unless... You are planning on using them for something else. Are you? I also changed the `README` from or `.org` (Org-Mode) to `.md` (MarkDown). I find MarkDown a little more cleaner and universal then Org-Mode and not only that but Githubs default `README` begins as MarkDown. Again, along with the key-bindings, this is up for debate. Org-Mode or MarkDown?