Koans submission mode added to submit program.

Possible solution to Issue #65
I don't know if we need to special case this logic just for "koans mode".

Maybe it would be better to change the logic of `Submit` program to: 
   * If the user specifies a directory on the command line, submit all of the `.java` files that reside beneath that directory.
   * Allow the user to submit `.java` files that reside in the `beginner`, `intermediate`, and `advanced` directories in addition to `edu/pdx/cs410J/<username>` directory.