Log Message:
py-fonttools: updated to 3.18.0

3.18.0 (released 2017-10-30)
[feaLib] Fixed writing back nested glyph classes.
[TupleVariation] Reactivated shared points logic, bugfixes.
[AAT] Implemented morx ligature subtables.
[reverseContourPen] Keep duplicate lineTo following a moveTo.
[varLib.mutator] Suport instantiation of GPOS, GDEF and MVAR.
[sstruct] Fixed issue with unicode_literals and struct module in old versions of \ 
python 2.7