Account for floating-point error.

Fix:
	src/graphics.c
		-account for floating-point error inherent in drawBezier() and
		drawHermite(), which incremented a float t by 0.001 through the range
		[0, 1], by incrementing t by 1 in [0, 1000] and dividing by 1000 where
		necessary
		-define CURVE_STEP_PRECISION macro for the number of iterations each
		curve-rendering function executes (currently a 1000).