`.getCurrentState()` & `.setSingleSelectionRange()`

This is for #512.

It should return an object that contains the output of `rawHtml()` and perhaps the selection.
I made a change. Only the range will be kept in the state. This will keep the state object minimal. So it will be more like this:

```
var wym = jQuery.wymeditors(0);
var state = wym.getCurrentState();
wym.setSingleSelectionRange(state.selectionRange);
```