disable almost all vim settings

will re-enable as soon as I understand what they do
tmux.conf: cleanup trailing spaces
reduce initial columns for mvim windows
re-enable vim-session settings

disable auto{load,save}: very annoying when doing commits
disable all but known bundles

The idea is to re-enable them as soon as I understand their purpose
Rakefile: disable and comment

Disable ruby-related stuff while adding some comments explaining
what's being installed/configured