Test that suicide is not allowed
Test that it is possible to get a group of adjacent stones that are the same colour
Implement Board#groupStartingAt
Implement Board#oppositeColour
Test that it is possible to tell when a group has liberties
Implement Board#groupHasLiberties
Test that it is possible to get stones captured when making a particular move
Add missing return
Implement Board#stonesCapturedByPlay
Modify test helper to bypass Board rules
Only allow a stone to be placed if it has liberties