[vim] Indent vimrc comments further right

To allow space for longer configuration lines.
[vim] Remove smartindent, cindent

Remove smartindent and cindent from `.vimrc`.

Most of their functionality should be better provided by filetype
plugins, which will indent according to the filetype open.
[vim] Stop soft-wrapping RST documentation

Stop soft-wrapping RST documentation - it's probably best to keep it to
80 characters wide.
[vim] Spell-check RST and Markdown files
[vim] Add Goyo plugin

Add the Goyo plugin which provides a minimal interface for writing prose
in vim, much like 'zenroom':

https://github.com/junegunn/goyo.vim
Revert "[vim] Add vim-ansible-yaml plugin"

This reverts commit 5227c9910f29e325e80fabcb50385244e14b44f5.

I didn't find this plugin helpful as it indented Ansible actions to the
left of the 'name' for that action on the line above.
[vim] Set colorcolumn dynamically

Set the `colorcolumn` option using values relative to the `textwidth`
option, so that the columns highlighted will refresh as `textwidth`
changes.
[vim] Normalise autocmd options

Normalise `autocmd` options to make them consistent.
[vim] Move autocmd options together