Example with gulpfile

I believe this is an idiomatic example. However, two instances that should
be reviewed:

 - shell.task could be replaced with a child_process spawn (removing a dep
   on the shell package)

 - We should be able to return the pipe from the clean and build tasks
   rather than forcing the use of a callback to indicate synchronous
   steps. I wasn't able to get that to work though.

closes #82