Changed type of GridState from Array[Array[MineFieldState]] to
IndexedSeq[IndexedSeq[MineFieldState]]
Changed MineFieldGrid to reflect changes to GridState
Created type alias for difficulties and provided pre defined values
for easy, medium and hard in Difficulties object
Added uncoverPosition method to GridController
Merge branch 'master' of https://github.com/foobark/Meneswoper.git