added logging in parent thread

Hi @neekey

Thank you for the very useful tool. I am building a complex integration and build tool, and grunt-multi is a key component! I noticed one strange behavior: The ``logBegin`` message does not appear in the output until each child process finishes. I think that this is because the output from the child processes is not being written to the stdout of the parent process until the child exits. 

I am providing a simple fix here that prints the ``logBegin`` message from lib.utils.js before spawning the child process. 

This probably adds functionality that is too specific into utils.js, but I don't see any other way. I did already try adding the stdio: 'inherit' property to the spawn process with no success, but am open to suggestions.