Fixed an incorrect casting from list to Card

While trying to create a relevant-cards-only hand, we accidentally were
changing the list INTO the only relevant card in a high-card hand.

This commit changes this to create a new list with ONLY the high-card in
it

Fixed beli-sk/pokercards#1
Merge pull request #2 from travisby/master

Fixed an incorrect casting from list to Card (Issue #1)