Update README.md instructions and formatting

Add a first step to explicitly start the Zsh shell, as some issues were
reported before because users were skipping this. See #214 for example.

Also mention `~/.zlogin` as part of the uninstalling process.

Use the following formatting styles:
* Headers >1 are in `Sentence case`.
* The names `Zim` and `Zsh` always appear capitalized, even in the
  middle of sentences.
* Prefer

      code indented with 4 spaces

  instead of
  ```
  code fenced by lines with three back-ticks
  ```

Closes #315

README.md

@@ -1,5 +1,5 @@
-ZIM - Zsh IMproved
+Zsh IMproved FrameWork
-==================
+======================
 
 <div align="center">
   <a href="https://github.com/zimfw/zimfw">
@@ -26,10 +26,10 @@ For a speed comparison between Zim and other frameworks, see [this wiki entry][s
 
 To preview some of the available themes, check the [themes wiki page][themes].
 
-### Fish-shell History Navigation
+### Fish-shell history navigation
 ![history-substring-search][fish_shell]
 
-### Syntax Highlighting
+### Syntax highlighting
 ![syntax-highlighting][syntax_highlighting]
 
 ### And much more!
@@ -40,56 +40,53 @@ Installation
 Installing Zim is easy. If you have a different shell framework installed (like oh-my-zsh or prezto),
 *uninstall those first to prevent conflicts*. It can be installed manually by following the instructions below:
 
-1. In a Zsh shell, clone the repository:
+1. Start a Zsh shell:
-  ```
+
-  git clone --recursive https://github.com/zimfw/zimfw.git ${ZDOTDIR:-${HOME}}/.zim
+       zsh
-  ```
+
+2. Clone the repository:
+
+       git clone --recursive https://github.com/zimfw/zimfw.git ${ZDOTDIR:-${HOME}}/.zim
+
+3. Paste this into your terminal to prepend the initialization templates to your configs:
 
-2. Paste this into your terminal to prepend the initialization templates to your configs:
-  ```
        for template_file in ${ZDOTDIR:-${HOME}}/.zim/templates/*; do
          user_file="${ZDOTDIR:-${HOME}}/.${template_file:t}"
          cat ${template_file} ${user_file}(.N) >! ${user_file}
        done
-  ```
 
-3. Set Zsh as the default shell:
+4. Set Zsh as the default shell:
-  ```
+
        chsh -s =zsh
-  ```
 
-4. Open a new terminal and finish optimization (this is only needed once, hereafter it will happen upon desktop/tty login):
+5. Open a new terminal and finish optimization (this is only needed once, hereafter it will happen upon desktop/tty login):
-  ```
+
        source ${ZDOTDIR:-${HOME}}/.zlogin
-  ```
 
-5. You're done! Enjoy your Zsh IMproved! Take some time to read about the [available modules][modules] and tweak your `.zshrc` file.
+6. You're done! Enjoy your Zsh IMproved! Take some time to read about the [available modules][modules] and tweak your `.zshrc` file.
 
 Updating
 --------
 
-To update zim, run:
+To update Zim, run:
 
-```
+    zmanage update
-zmanage update
-```
 
 For more information about the `zmanage` tool, run `zmanage help`.
 
 Uninstalling
 ------------
 
-The best way to remove zim is to manually delete `~/.zim`, `~/.zimrc`, and
+The best way to remove Zim is to manually delete `~/.zim`, `~/.zimrc`, and
-remove the initialization lines from your `~/.zshrc`.
+remove the initialization lines from your `~/.zshrc` and `~/.zlogin`.
 
-However, there are some **experimental** convenience functions to remove zim:
+However, there are some **experimental** convenience functions to remove Zim:
 
 **NOTE: This functionality is experimental!**
 
-To remove zim, run:
+To remove Zim, run:
-```
+
-zmanage remove
+    zmanage remove
-```
 
 **NOTE: This functionality is experimental!**