create plugin for automatic setting of paste mode

Create a plugin to automatically set paste mode in vim
when in insert mode.

The aim is to avoid having to call ``set paste``
and ``set nopaste`` or to use ``pastetoggle``.

The script was written by Marcin Kulik; see https://coderwall.com/p/if9mda
update doc for vim-autosetpaste
Merge branch 'master' of https://github.com/saliola/dotvim