[outlineCompiler] copy width attribute when convertCubics=True (needed for autoUseMyMetrics)
[outlineCompiler] copy width attribute when convertCubics=True (needed for autoUseMyMetrics)

Fixes https://github.com/googlei18n/ufo2ft/issues/136

googlei18n/ufo2ft,jamesgk/ufo2fdk,googlefonts/ufo2ft,jamesgk/ufo2ft,moyogo/ufo2ft