Prints out a spiral. Supports square and rectangular matrices.
var s = new Spiral(numRows, numCols);
s.print()
XX
-X
XXX
--X
XXX
XXXX
---X
X--X
XXXX
XXXXX
----X
XXX-X
X---X
XXXXX
XXXXXXXXX
--------X
XXXXXXX-X
X-----X-X
X-XXX-X-X
X-X---X-X
X-XXXXX-X
X-------X
XXXXXXXXX
XXXXXXXXXXXXXXXXXXXX
-------------------X
XXXXXXXXXXXXXXXXXX-X
X----------------X-X
X-XXXXXXXXXXXXXX-X-X
X-X------------X-X-X
X-X-X----------X-X-X
X-X-XXXXXXXXXXXX-X-X
X-X--------------X-X
X-XXXXXXXXXXXXXXXX-X
X------------------X
XXXXXXXXXXXXXXXXXXXX