v2.1.0b4

What's Changed

• Fix for issue https://github.com/o-murphy/py-ballisticcalc/issues/141… by @serhiy-yevtushenko in #143
• __config bind refactoring for cythonic TrajectoryCalc by @o-murphy in #142
• Handle trajectories that bend backwards. by @dbookstaber in #139
• Added helpers, test_helpers files and add_time_of_flight_axis method … by @serhiy-yevtushenko in #146
• 147 trusted publishers by @o-murphy in #148
• bump-2.1.0b4 by @o-murphy in #149

Full Changelog: v2.1.0b3...v2.1.0b4