What's Changed
* Adding gamma plotter by shimwell in https://github.com/fusion-energy/openmc_source_plotter/pull/23
* method instead of class by shimwell in https://github.com/fusion-energy/openmc_source_plotter/pull/28
* removed old setup method by shimwell in https://github.com/fusion-energy/openmc_source_plotter/pull/29
* updated readme with gammas spec image by shimwell in https://github.com/fusion-energy/openmc_source_plotter/pull/30
**Full Changelog**: https://github.com/fusion-energy/openmc_source_plotter/compare/0.6.2...0.6.3