Adding Go to Edit Point functionality

After years using Sublime Text, I felt quite uncomfortable lacking "Go to Edit Point" feature, so I implemented it myself. 
The solution might not be perfect or beautiful, but it works precisely like Emmet core functions. Moreover, it supports number prefixes (like `C-5 M-C-right`), which feels natural in Emacs environment.

P.S. A whole lot of Emmet standard actions are not implemented yet, such as [Match Tag Pair](http://docs.emmet.io/actions/match-pair/) and [Wrap with Abbreviation](http://docs.emmet.io/actions/wrap-with-abbreviation/). I think this is a flaw of emmet-mode, and I think that we should make some effort to implement at least the most useful of Emmet core features. I'm going to do something about it in the near future.