Fix Cards.String() and Card.String()
Fix issue with histogram.getCardsByFrequency()

When iterating over the Cards items in the histogram, return
a deep copy, not a pointer during the for loop.
Merge pull request #3 from miniharryc/master

MergeHarold's fixes

Fix for nasty bug with comparing hands of equal ranks, added Duffy's suggestion for Ace-low straights