allows the statusline to be customised for the nerd tree window

*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

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

Do an unlet <old key> when over riding a method on a prototype object.
Some older versions of vim spaz out otherwise.

Note: i was using these unlets up until a few versions ago when the were
refactored out

put all the option help tags in single quotes

now we dont assume the cursor is in the nerd tree window when calling
s:SaveScreenState()

invalid bookmarks now placed after a blank line at the bottom of the
bookmarks file

if invalid bookmarks are detected, an error is outputted which directs
the user to :help NERDTreeInvalidBookmarks, which had been added to the
help file in this commit

we dont need it to default to 1 anymore as that was a hack for windows,
but now that we handle windows paths properly we dont need it

when the user hits B and opens the bookmarks table, stick the cursor at
the top of it

make the t/T on directory nodes open a fresh NERD tree for the selected
dir in a new tab, rather than a netrw.

when opening a file in a new split (with the <tab> map) we were doing
the :split with a "silent" modifier. This meant that a swap existed and
input was required from the user, the script would just freeze up