pimping vimperator usage

* adding .vimperatorrc to disable qq key and activate proper editor
  usage
* cleaned up gvimrc a little
* readded mvim script to start Macvim from vimperator
adding bind for marking message as spam; additional alias settings
using html2text.py for viewing text/html mails in mutt
added syntac highlighting for vimperatorrc
removing unused file
adding vim-tmux-navigator for better navigation between splits
adding vim-indent-guides plugin
finally getting html mails to work properly in mutt
adding new key mapping for toggling insert paste mode