Make FontProject.preprocess a @staticmethod
Make FontProject.preprocess a @staticmethod

Such that it can be called by other code.

IMO the functionality of that function should be moved to glyphs2ufo.
Also see: https://github.com/behdad/fonttools/issues/559

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