[doc] Update beginners_tutorial.org todo key, etc.

The org-mode todo key has been changed from just: t
to: SPC m T T (same as: , T T)
in this PR: Use evil-org from MELPA #9041

The PR authors reasons were:
>- single-shortcut keys are few in number and valuable
>- the vim/evil defaults for those keys are designed for editable modes, and org
>  is an editable mode
>- practically nowhere else in Spacemacs are such keys overridden
>- the benefit of making an exception in this case is dubious
>- it's not too difficult to configure on a user level
>
>For sure, many people will be toggling todo state more often than using the t
jump operator while in org-mode, but I'm not convinced that this is worth
violating POLA in org-mode. But of course if there is consensus that I'm wrong
then I'm happy to be convinced otherwise.

source: https://github.com/syl20bnr/spacemacs/pull/9041#issuecomment-309758098

- Mentioned that: `t` can be restored for toggling todo, and added a link to the
  instructions in the org layer documentation:
  https://github.com/syl20bnr/spacemacs/blob/develop/layers/%2Bemacs/org/README.org#org-with-evil-org-mode
- Rewrote some sentences.
- Wrapped some paragraphs at 80 chars.

doc/BEGINNERS_TUTORIAL.org

@@ -36,9 +36,9 @@ using a program called Git. The steps are easy and detailed in the [[https://git
 
 * Getting started
 ** Key binding notation
-The power of Spacemacs lies in its efficient key bindings. Because it is built on
+The power of Spacemacs lies in its efficient key bindings. Because it is built
-Emacs, we will use Emacs conventions for key binding notation. The most important
+on Emacs, we will use Emacs conventions for key binding notation. The most
-modifier keys are:
+important modifier keys are:
 
 ~SPC~ = ~Space~, used as the leader key in Vim editing style.
 ~RET~ = ~Return~ (also known as ~Enter~)
@@ -164,13 +164,13 @@ Spacemacs divides its configuration into self-contained units called
 configuration layers. These layers are stacked on top of each other to achieve a
 custom configuration.
 
-By default Spacemacs uses a dotfile called =~/.spacemacs= to control which layers
+By default Spacemacs uses a dotfile called =~/.spacemacs= to control which
-to load. Within this file you can also configure certain features. First, split
+layers to load. Within this file you can also configure certain features. First,
-the window vertically to view both this tutorial and the dotfile simultaneously
+split the window vertically to view both this tutorial and the dotfile
-(~SPC w /~). Open the dotfile by pressing ~SPC f e d~. Navigate to the line
+simultaneously (~SPC w /~). Open the dotfile by pressing ~SPC f e d~. Navigate
-starting with "dotspacemacs-configuration-layers". The following lines have
+to the line starting with "dotspacemacs-configuration-layers". The following
-further instructions: uncomment =org= and =git= layers if you want to be
+lines have further instructions: uncomment =org= and =git= layers if you want to
-familiarized with them. More [[https://github.com/syl20bnr/spacemacs/blob/develop/doc/LAYERS.org][layers]] for different languages and tools can be
+be familiarized with them. More [[https://github.com/syl20bnr/spacemacs/blob/develop/doc/LAYERS.org][layers]] for different languages and tools can be
 found by pressing ~SPC h SPC~. The added layers will be installed upon restart
 of Spacemacs.
 
@@ -183,8 +183,8 @@ activated themes. You can find more by adding the themes-megapack layer and
 activate them by writing their names in the dotspacemacs-themes list.
 
 ** Starting maximized
-Editing the =dotspacemacs-maximized-at-startup= variable from =nil= to =t= will start
+Editing the =dotspacemacs-maximized-at-startup= variable from =nil= to =t= will
-Spacemacs maximized.
+start Spacemacs maximized.
 
 ** Quitting
 Save the changes you've made to the dotfile with ~SPC f s~ and then quit emacs
@@ -199,18 +199,20 @@ and effective plain-text system", but this gives only a small inkling of its
 versatility. If you do any kind of writing at all, chances are that Org mode
 will make it easier and more fun. This tutorial was written in Org mode.
 
-Install the Org layer and open this tutorial. Make a copy named test.org with
+To test some of it's features. Install the Org layer and open this tutorial.
-~SPC f c~ somewhere outside of the .emacs.d directory. Write
+Make a copy named =test.org= with ~SPC f c~ somewhere outside of the =.emacs.d=
-~SPC SPC org-mode RET~ to switch to org mode from the write-only documentation mode.
+directory. Press ~SPC SPC~, write ~org-mode~ and press ~RET~ to switch to
+=org-mode= from the write-only documentation mode.
 
 Press ~S-TAB~ repeatedly and observe that this cycles the visibility of the
-contents of different headlines. Press ~t~ in normal mode and observe that you
+contents of different headlines. Press ~SPC m T T~ in normal mode and observe
-can add TODO tags on headlines. Press ~M-k~ or ~M-j~ in normal mode and see how
+that you can add TODO tags on headlines. (This can be changed to just ~t~, see
+the [[https://github.com/syl20bnr/spacemacs/blob/develop/layers/%252Bemacs/org/README.org#org-with-evil-org-mode][org]] layers documentation). Press ~M-k~ or ~M-j~ in normal mode and see how
 you can quickly move parts of the document around.
 
 This is not even scratching the surface of Org mode, so you should look into
 [[https://github.com/syl20bnr/spacemacs/blob/develop/layers/%2Bemacs/org/README.org][org layer]] with ~SPC h SPC org~ for more information. Googling for Org mode
-tutorials is also very helpful in finding out the most useful features of it!
+tutorials is also very helpful for finding out about the most useful features!
 
 ** Version control - the intelligent way
 Version control means keeping track of the changes and edits you have made to