Added test for Issue 20.  Which fails (although not in a particularly relevant way).
Added test for Issue 20.  Which fails (although not in a particularly
relevant way).


git-svn-id: 319eb561774c901116a2c19d0db24e717df3a3eb@25 40d66c6c-0ee5-11de-8837-45bce846067a

drj11/pypng,Scondo/purepng,drj11/pypng,mnaberez/pypng,Scondo/purepng,mnaberez/pypng