Don't do interpolation in glyphsLib
Don't do interpolation in glyphsLib

I'd prefer that glyphsLib not do any interpolation, especially since
we have code to do it here in fontmake anyways. So don't use
glyphsLib's interpolation in fontmake as a first step.

googlei18n/fontmake,googlefonts/fontmake,googlei18n/fontmake,googlefonts/fontmake