Add arrows for entering and exiting points of a Dubins Path

[katzuv]

The Python program right now plots the point. What I would like to have is two arrows pointed in the direction the robot enters and exits a Dubins Path. I think that might be pretty easy if the Python program could know what are the centers of the two circles. That's because the direction is tangent to the circle and a tangent to a circle is perpendicular to the radius which goes from the center to the tangent point. @pauloalbert, what do you think?

[katzuv]

the more issues i get through the sadder i get about pure pursue dying