doesn't work with the new version of opencv

[AlexandreDewilde]

cv2.findContours() has been changed in the new version of opencv
https://github.com/akshaychandra21/Selfie_Filters_OpenCV/blob/9dd59ae72716fe25370ff2a396bc812b42766f69/shades.py#L48
Should add a requirements.txt file or fix like this (cnts, _) = cv2.findContours(blueMask.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)