move a couple of functions into NERDTreeCreator

The "next buffer name" functions are only used in NERDTreeCreator so put
them there.
catch an error thrown when refreshing a dir with a FIFO or socket
fix NERDTreeCWD

Closes #233
fix a bug where the user couldnt override the mapping for <cr>
move the class files out of the plugin dir

On some new versions of vim these files were being loaded before the
main NERD_tree.vim which was causing errors as dependencies werent
loaded in time. Move the classes into lib - so vim wont try to load them
until we tell it
don't redefine user-defined mappings

As a user it's a little jarring when a plugin maps over something I've
already defined.  This patch fixes that problem, by using `<unique>` to
ensure unique mappings.

For more info see `:help <unique>`

Note: This has no effect if the mapping isn't already defined (that is,
NERDTree is defining a unique mapping), so this won't break for normal
users of the plugin.

Note: `:silent!` is needed to ignore the error that occurs when a
mapping is already defined.

Fixes #252
Merge pull request #255 from joshuarh/unique-mappings

don't redefine user-defined mappings
Revert "don't redefine user-defined mappings"

This reverts commit 2fa35fb4949f670f1c137dc26a779f6e0515b330.
fix spelling in documentation
Merge pull request #263 from medvid/master

Fix spelling errors in documetation
Fixed typo in NERD_tree.txt
Fix help mistake
Create nested parent directories as needed

Allows the user to create or copy a nested node
in a single step with ma or mc, recursively
creating nested parent directories if needed, and
without throwing any errors if they already exist.

[Finishes #163, #34]
Fix typo
Add option to respect wildignore
correct invalid reference to MenuController

I found an error when I tried to use [git_menu.vim](g:NERDTreeMenuController):

```
Error detected while processing function nerdtree#invokeKeyMap..91..90..<SNR>52_showMenu..65..82:
line    2:
E121: Undefined variable: s:MenuController
E15: Invalid expression: s:MenuController.New(self.children)
line    3:
E121: Undefined variable: mc
```

I searched the line at which it happened
then, I found that `s:MenuController` is not defined in  `menu_item.vim` but in menu_controller.vim .
So I corrected the name to refer to MenuController.
Issue 315 - Incorrect buffer deleted on file delete
Use pathogen.vim Helptags command in README file
Add flag to disable/enable bookmark sorting

The bookmarks are normally sorted, however with a newly introduced
flag this can be disabled.
Support space in path when renaming