added features/bug fixes headings to changelog
added features/bug fixes headings to changelog

USGSDenverPychron/pychron,UManPychron/pychron,UManPychron/pychron,UManPychron/pychron,NMGRL/pychron,NMGRL/pychron,USGSDenverPychron/pychron,USGSDenverPychron/pychron,USGSDenverPychron/pychron,NMGRL/pychron,NMGRL/pychron,UManPychron/pychron