Add recursive add command
Add recursive rm command
Add recursive one-shot command

To keep this somewhat tidy: requires changing the `*)' case to either read
from either ~/.multigit or /dev/stdin depending on whether we are
piping or not.
Change mgit back to mg

Totally forgot that I changed the function name from mg to mgit in my system (my editor is `mg'). Accidentally left the references as mgit in the bash commands.
Merge pull request #1 from philipdexter/master

Some recursive nonsense