Enable full path specifications for NERDTreeIgnore (#1207)

* Add ability to specify a path to be ignored.

This ignore expression compares itself against the whole path of the
node, instead of just the tail component of the node.

* Remove debug statements and make it work on Windows.

* Restore the original self.str() to get OS-specific paths for comparing.

Using the UI-formatted path had two problems.
1. It always appended a forward slash at the end of the path, which was
   unnecessary and made patterns like '/tmp/cache$[[path]]' not work as
   expected.
2. It always used forward slashes to join the path components. I thought
   this would be a good thing, but there's no reason to force Windows
   users to use that syntax. They'll just need to remember to escape the
   backslashes, like so: '\\Temp\\cache$[[path]]'

* Add documentation for the new [[path]] tag for NERDTreeIgnore.

* Replace the abbreviation 'dir' with the full word 'directory'.

* Update version number in change log.

lib/nerdtree/path.vim

@@ -483,7 +483,10 @@ endfunction
 " returns true if this path matches the given ignore pattern
 function! s:Path._ignorePatternMatches(pattern)
     let pat = a:pattern
-    if strpart(pat,len(pat)-7) ==# '[[dir]]'
+    if strpart(pat,len(pat)-8) ==# '[[path]]'
+        let pat = strpart(pat,0, len(pat)-8)
+        return self.str() =~# pat
+    elseif strpart(pat,len(pat)-7) ==# '[[dir]]'
         if !self.isDirectory
             return 0
         endif