vimrc: move autocommands before early exit.

The autocommands need to come before the colorscheme declaration, as
otherwise Vim produces errors in some cases.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
vimrc: don't call any functions if we're exiting early.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>