Add a new method to convert from RGB to HSV

Create a method to convert from RGB to HSV easily in Python.
The main purpose is to call the function "inRange" of cv2.
Example with the GOLD one:
hsv_image = cv2.cvtColor(blur_image, cv.CV_BGR2HSV)
threshold_image = cv2.inRange(hsv_image, np.array((23., 100., 100.)), np.array((27., 255., 255.)))