Vim again :-): Bindings; Spell-checking; Plugins

* Un-silence all my bindings (for now at least, whilst I get the hang...)
* Explicitly set smartcase for nicer searches
* Explicitly unset spell-checking in help files
* Start using fugitive.vim
* Use continuation lines to make whitespace settings clearer
* Clean up gvimrc
* Fix issue with MacVim not seeing .md files as Markdown
* CHANGES files are text files (causes them to be spell-checked)
* Force background to be properly black, despite molokai
Vim Whitespace Stuff

* Use the 'better whitespace' plugin
* Update my bindings and config to use the plugin and not previous stuff
* Re-structure my vimrc
* Clarify difference between whitespace and non-printing characters