Remove some redundant plugins

Unite is supposed to be amazing but I have not found an adequate
explanation of why. It is much much slower than ctrl-p.

The multiple cursor plugin is a nice try, but is too limited compared to
normal vim use.
Update vim readme

Covers all current plugins
Move vim settings into plugin

The non plugin dependent settings are now in their own plugin. The vimrc
will just control the plugins. Then can have a lite / normal / heavy
vimrc for different machines.