Save/Set screen state also on WinLeave and WinEnter. (#1048)

* Save/Set screen state also on WinLeave and WinEnter.

The particular use case here is when switching tabs with `gt` and the
NERDTrees have been mirrored.

* Update version number and change log.

CHANGELOG.md

@@ -1,6 +1,7 @@
 # Change Log
 
 #### 6.1...
+- **.3**: Save/Set screen state also on WinLeave and WinEnter. (PhilRunninger) [#1048](https://github.com/scrooloose/nerdtree/pull/1048)
 - **.2**: Wrap saveScreenState's statements in a try-catch block. (PhilRunninger) [#1047](https://github.com/scrooloose/nerdtree/pull/1047)
 - **.1**: Catch errors when trying to read CHANGELOG.md. (PhilRunninger) [#1045](https://github.com/scrooloose/nerdtree/pull/1045)
 - **.0**: If file path doesn't exist, :NERDTreeFind its parent directory instead. (PhilRunninger) [#1043](https://github.com/scrooloose/nerdtree/pull/1043)

plugin/NERD_tree.vim

@@ -170,10 +170,10 @@ call nerdtree#ui_glue#setupCommands()
 "============================================================
 augroup NERDTree
     "Save the cursor position whenever we close the nerd tree
-    exec "autocmd BufLeave ". g:NERDTreeCreator.BufNamePrefix() ."* if g:NERDTree.IsOpen() | call b:NERDTree.ui.saveScreenState() | endif"
+    exec "autocmd BufLeave,WinLeave ". g:NERDTreeCreator.BufNamePrefix() ."* if g:NERDTree.IsOpen() | call b:NERDTree.ui.saveScreenState() | endif"
 
     "disallow insert mode in the NERDTree
-    exec "autocmd BufEnter ". g:NERDTreeCreator.BufNamePrefix() ."* stopinsert"
+    exec "autocmd BufEnter,WinEnter ". g:NERDTreeCreator.BufNamePrefix() ."* stopinsert"
 augroup END
 
 if g:NERDTreeHijackNetrw