directory tree sidebar for Emacs that is like NERDTree for Vim

 NeoTree is a modern, themeable alternative to the Emacs builtins
 Dired and Speedbar. Like Speedbar, it auto-refreshes without needing
 to type "g". Like Dired, but unlike Speedbar, it creates a new
 window as a sidebar and not a whole new frame (eg: not a new X11
 application window with its own window decorations). NeoTree shows a
 file system tree relative to the users' $HOME, where both Dired and
 Speedbar default to showing the contents of the current directory.
 Thus it provides a hierarchical rather than a modal view.
 .
 Neotree is similar to Vim's NERDTree plugin.
 .
 This addon is for users who are more comfortable with the directory
 tree sidebar/file system explorer used in most non-Emacs applications.