Path.New was expecting an absolute path. Now we convert paths to
absolute inside Path.New

make sure we always go back to the right buffer, and if there is no
buffer to go back to, close the window

since we are now ":edit"ing a new buffer for secondary nerd trees, we
have to store the previous buffer number otherwise we get into an
infinite loop because we go back to a directory buffer which causes
another secondary nerd tree to open etc

*remove the change log prior to v3.0.0
*remove the todo section
*change "about the author" to "about" and put the github/vim.org project
urls in it

if we were using e on the current dir (or a file in that dir) then we
would end up doing an ":edit" with no target. Now we use "." in
Path#strForEditCmd if it would resolve to an empty string

Use a sequential numbering system instead of timestamps. This makes the
buffer names shorter and neater and easier on the eye when using
:NERDTreeMirror

remove "top" and "bottom" as valid settings for NERDTreeWinPos