add clipart originator usernames to CONTRIBUTORS #45

CONTRIBUTORS.md

@@ -25,6 +25,7 @@ These people have contributed to Calagator's design and implementation:
   * Don Park
   * Donald Plummer
   * Ed Borasky
+  * [frankes](http://openclipart.org/user-detail/frankes)
   * Gabrielle Roth
   * Igal Koshevoy
   * Jeff Schwaber
@@ -57,5 +58,6 @@ These people have contributed to Calagator's design and implementation:
   * Seve Salazar
   * Ted Kubaska
   * Ward Cunningham
+  * [yves_guillou](http://openclipart.org/user-detail/yves_guillou)
 
 Facilities for many code sprints were generously donated by [Cubespace](http://cubespacepdx.com/), "an innovative workspace community in Portland, Oregon. We provide work stations, meeting rooms, and big office amenities to people who would otherwise be working from their homes, coffee shops, or wherever they can set up their laptops or use their cell phones"