bump to 9.7.0

add youtube, discord, humble buttons (#1292)

sign windows 7 version (#1291)

add webp output support (ignored for Kindle MOBI/EPUB and all PDF) (#1290)

disable extra png options when png is not selected (#1289)

smart cover crop is now an option default off (#1288)

revert 2x render, too expensive (#1287)

ZIP stored instead of deflate (#1283)

if cropping, render pdf to 2x (#1276)

Update __init__.py

fix autocrop in certain situations (#1274)

bump 9.6.1

fix humble bundle pdf png autocontrast (#1273)

color images are always saved as JPG by default (#1272)

add PNG legacy option (#1271)