The much needed /me command

_The following is copied from #723_

In a perfect world, I'd know where to call a code page that would allow for slash commands to be easily created by users- eg 
```javascript
WikiaChatCommands.create("/foo", function () {});
```
But I don't know where to call that page so I have to do with adding a small if to processText that adds a /me command.

Thanks.