MikeHeiber/Ising_OPV: Tortuosity Histogram Bugfix

This update fixes a bug that was causing the tortuosity probability histogram output to be missing data for the first bin of the histogram. For a detailed account of all changes, please see the Changelog.

This release was developed under the financial assistance award 70NANB14H012 from U.S. Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Materials Design (CHiMaD).