Fixed bug in derivative.
Merge pull request #44 from luca-heltai/fix-derivative-iterated

Fixed bug in derivative.
arclength_curve v1.0

fixed arclenght_curve test

Cleaning arclength_curve
Application of arclenght_curve

applications/animation.mp4 has been removed

applications/lib/__init__.py

arcLength_curve

font.py is required by progress_bar