Make neotree stick on left.
Merge pull request #8 from jianingy/sticky-tree

Make neotree stick on left.
NeoTree with fixed width
Merge pull request #9 from jianingy/fixed-neotree

NeoTree with fixed width
Fix Issue #7
Merge pull request #11 from jianingy/fix-open-window

Fix Issue #7
doc string of global functions
mouse drag to resize neotree window.
fix: toggle failed when use fixed width.