Make #wmd-button-bar non-required

```
I use pagedown also in comment-form it has well keyboard shortcuts support,
it's very useful to format small code snippets against typing 4 spaces every
single line. But I have to put button bar on dom also. Of course I can hide it
with css but that's not on true-way.

There are some other issues I want to post if you don't mind. Actually for now
there is no any other editor to be used with markdown except markitup — which
as to me very is very weird and do everything but nothing well.
```

Original issue reported on code.google.com by `byashi...@gmail.com` on 11 Feb 2012 at 4:59