Edit preview images and fix bounding boxes in EPS files

Current version

epstool requires the following formula to be installed:
ghostscript 9.21_4 Interpreter for PostScript and PDF

Formula history

Dominyk Tiller epstool: use homebrew mirror
Nikolaus Wittenstein Add descriptions to all remaining homebrew packages
Xu Cheng epstool: add test and missing runtime dependency
Dominyk Tiller epstool: replace failing url