Add error handling if currentX and currentY are not aligned with unit spaces

[nashirj]

moveStraight and moveDiagonal assume that the EM is aligned with a unit space. Should add a check to those functions to make sure that we are aligned before moving.

// Before starting movement
if ((currentX % stepsPerUnitSpace) || (currentY % stepsPerUnitSpace)) {
    // Align to a unit space or raise an error or something
}