Add ability to set a message when sending a command

[bew]

When commands are executed on other shells, it looks like:
zc-all source /foo/bar
and on other shells:
source /foo/bar ##

I think it would be nice to have:
zc-all -m "reload stuff" source /foo/bar
and on other shells:
source /foo/bar ## reload stuff

(which is even better when using syntax highlighting)