Added alias: rb for rebase

dotfiles/git-universe/before.gitconfig

   com = checkout master
   dc = diff --cached
   gr = log --graph --full-history --all --color --pretty=tformat:"%x1b[31m%h%x09%x1b[32m%d%x1b[0m%x20%s%x1b[0m"
+  rb = rebase
   rbi = rebase --interactive
   rmv = remote --verbose
   st = status