Make these all go through .open() and pass in args to control the behaviour. Deprecate the old `openSplit`, `openVSplit` and `openInNewTab` methods and make them private. This makes the API a lot cleaner - it was getting pretty messy in this regard.
This fixes #89.
Just call these functions directly at the bottom of the nerdtree script. This simplifies things and fixes #99.
create s:setCommonBufOptions() with the previously duplicated parts of s:initNerdTreeInPlace() and s:createTreeWin()