Added check to drawVertical() and drawHorizontal() to cover the issue of drawing over already drawn lines.
Altered the return value of boxComplete() to return the conjunction of the state for each line of the box.

drawingAHorizontalLineOverAnAlreadyDrawnLineShouldThrow() handles the issue of the illegal operation of drawing over a line that has already been drawn.

callingboxCompleteOnACompleteBoxShouldReturnTrue() tests the correct state of boxes being complete when completely surrounded by lines.

callingboxCompleteOnAnIncompleteBoxShouldReturnFalse() tests the correct state of boxes not being complete until they are completely surrounded by lines. This will progressively surround a box, testing at each step to ensure that the box is not complete until all 4 lines are drawn around the box.

0.0.10 seems to have fixed the issue with running modular JavaFX
  projects, allowing us to drop the previous (manual) fix.