Add edit abstraction to sublime_lib

Obtained from
https://github.com/lunixbochs/SublimeXiki/blob/st3/edit.py
and slightly modified.
Update sublime_lib to ST3

Add a bunch of utility methods to get the current package/module
path/name which work for both ST2 and ST3.
Add separate yaml package for Python 3
Update other Lib modules to changes
Update plugin files to work with ST3
Remove setup.py

The last time it was used was probably 2 years ago and it always gets
loaded by ST.
Make imports work when in .sublime-package
Fix problems when rearranging

I'm 100% sure I fixed these already, must've gotten lost somewhere.
Less debugging
Merge pull request #38 from FichteFoll/st3-compatible

ST3 compatibility