Rename before.gitconfig to more sane main.gitconfig

dotfiles/gittum/bin/setup

 user=`whoami`
 
 printf "[include]\n" >> ~/.gitconfig
-printf "    path = $tilde/.gittum/before.gitconfig\n" >> ~/.gitconfig
+printf "    path = $tilde/.gittum/main.gitconfig\n" >> ~/.gitconfig
 printf "    path = $tilde/.gittum/host/$host.gitconfig\n" >> ~/.gitconfig
 printf "    path = $tilde/.gittum/user/$user.gitconfig\n" >> ~/.gitconfig
 printf "    path = $tilde/.gittum/private.gitconfig\n" >> ~/.gitconfig