Round this decimal away from zero, to the next whole number.
Examples:
(-0.4).ceil() returns -1
(-0.4).ceil()
-1
(-1.99999).ceil() returns -2
(-1.99999).ceil()
-2
(1.99999).ceil() returns 2
(1.99999).ceil()
2
(1.00000000000000000001).ceil() returns 2
(1.00000000000000000001).ceil()
0.9.1