Test.

Added a test for flush.
Implementation.

Added code for flush. Even simpler than straight.
Test.

Added a test for full house. It identifies the hand as a three-of-
a-kind, not surprisingly.
Implementation.

Implementation for full house. Thinking about whether or not I should
add the score of the pair as well.
Test.

Added a test for four-of-a-kind. Hand is identified as three-of-a-kind
now.
Implementation.

Added code for four-of-a-kind. Basically a copy of three-of-a-kind
which again points to the opportunity for refactoring.