Adapted emmet-html-next-insert-point to use emmet-go-to-edit-point

Issue https://github.com/smihica/emmet-mode/issues/35
Rewrote `emmet-html-next-insert-point` completely, now it reuses `emmet-go-to-edit-point` and looks much simpler.
Also, removed some bugs and unnecessary bindings from `emmet-go-to-edit-point` itself.
I didn't take care about not putting cursor after closing tag, though. But, surprisingly, I couldn't reproduce the behavior @pobocks mentioned in issue, because for me that
```
div/+div
```
expands into that
```html
</div>
<div>|</div>
```
e. g. it adds a newline after closing tag, automatically makes that place an invalid edit point.