minesweeper: Ensure test versioning consistency with other exercises (#527)
minesweeper: Ensure test versioning consistency with other exercises (#527)

* Moved TestTestFunction to top of test functions
* Errorf -> Fatalf

See #470
exercism/xgo,leenipper/xgo,robphoenix/exercism-go,leenipper/xgo,exercism/xgo,robphoenix/exercism-go