Speed up cubic resizing. Fix clamping.

Removed a branch from the x scaling hotpath by padding the scanline
before resizing.

Use the greatest common denominator of the scaling ratio numerator and
denominator to re-use scaling coefficients.

Fix value clamping by rounding up results that are very close to the
higher integer value. This offsets errors introduced by floating point
math.

Fix minitest deprecation warning.

Use sample format instead of components

use rgbx in ruby

Don't use doubles, convert everything to regular floats.

Added some fixed point math for scaling speedups.

Fix some zoom errors, png rupport for RGBX.

Up jpeg quality level to 90.