ttfonts.py: fix typo/bug in format2 reported by rmathot@bitbucket.org
textobject.py: fix bug in textlines contributed by Andrey Khomenko @ bitbucket.org
attempt to pacify pillow tostring warnings reported by Kale Franz @ bitbucket.org
_renderPM.c: allow aapixbuf destination to be floats
readme tweaks about windows installation
ttfonts.py: fix horizontal metrics (htmx table) computation
bump version to 3.1.15