MOPAC: An open-source semiempirical molecular orbital program

This patch release is synchronized with the acceptance of an open-source MOPAC release paper in the Journal of Open-Source Software (JOSS). It contains a few very minor bug fixes, and the main MOPAC distribution is now packaged with a set of basic examples of MOPAC calculations on the command line and through the recently released API. Another patch release will soon follow the publication of the JOSS paper with updated citation information, once the paper is available to be cited.