undo-tree-visualizer key mapping

Originally reported by: **Anonymous**

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The undo-tree-visualizer key remappings do not work for me. In particular:
```
undo-tree-visualize-redo
undo-tree-visualize-undo
```
Note that I have in my ```init.el``` (as recommended on several internet sites):
```
(define-key evil-normal-state-map (kbd " ") 'evil-next-visual-line)
(define-key evil-normal-state-map (kbd " ") 'evil-previous-visual-line)
(define-key evil-motion-state-map (kbd " ") 'evil-next-visual-line)
(define-key evil-motion-state-map (kbd " ") 'evil-previous-visual-line)
```
Maybe ```h,j,k,l``` should be remapped directly (or is there a better way to do the remapping to visual lines)? In addition, the help page is not helpful cause it shows the emacs commands primarily (some of which work, e.g. ```p```, and some don't, e.g. ```n```) and only the evil remappings at the bottom. Would it show the evil bindings directly if they actual keys are remapped?

Perhaps emacs mode should always be used for this buffer.

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- Bitbucket: https://bitbucket.org/lyro/evil/issue/408

Reproduce the mappings from init.el, then inspect the undo-tree-visualizer keymap and its help page while comparing Emacs and evil bindings. Determine whether remapped visual-line keys should work in the visualizer and whether the help should show the active evil bindings; done means the intended mappings work and the documentation is accurate.

Written by the indexing model from the issue text.