zshrc: Alias gl to git log -p

Signed-off-by: Carl Helmertz <helmertz@gmail.com>
vim: Don't use ctags

Autocompletion took ~20 seconds whilst editing php files and included
suggestions from js files etc =/ Ruby files were fine though. Since I
don't really use ctags, let's disable it for now.

Signed-off-by: Carl Helmertz <helmertz@gmail.com>