Sports2D: Compute 2D human pose and angles from a video or a webcam

• Post-processed angles better unwrapped and kept between -180 and 180°
• Displayed image is now in the correct ratio and as large as the screen allows
• added "sections_to_keep" argument (all, largest, first, last)
• Image indices used to be shifted back 1 frame
• when clicking the persons to analyze, the first annotation never disappeared
• no tracking when tracking mode is none (instead of sports2d tracking)
• Added clarification on angles in readme (flip_left_right, correct_segment_angles_with_floor_angle)

Full Changelog: https://github.com/davidpagnon/Sports2D/compare/v0.8.13...v0.8.14