Fix initial comment.
Retroactively add GPLv3 license.

Received permission via email from all authors / contributors listed in the
source:
 * Paul Eggert
 * Dave Probert
 * Andy Pippin
 * Jeff Sheltren
 * Stefan Karpinski
 * myself (Bryce Boe)
2014-09-03 Foivos S. Zakkak <foivos@zakkak.net>

   - Let tar ignore backup and vcs files
   - Fix arguments of tar to gunzip and not bzip
Merge with https://github.com/ucsb-cs/turnin.git

Commit (https://github.com/ucsb-cs/turnin/commit/fc1469ce6dddcba8d177f3f562e77ace785eb798)

Conflicts:
	turnin.c
Extend licensing.

 - Add -V --version flags
 - Add Copyright notices with the contributors)