Add popwin support through around advices
rename inner functions
Add support for window selection via window-numbering

Example:
To open a node in window number 2 press: 2-RET
Merge pull request #65 from syl20bnr/popwin-support

Add popwin support through around advices
Merge pull request #66 from syl20bnr/window-numbering-support

Add support for window selection via window-numbering
When neotree-window is created, do not auto select