Added a panel for the convexulation homework.
Added a function to test whether a given segment between two vertices of
the polygon intersects any other side of the polygon. (chordCrosses)
Added a function to test whether a segment form vertex v to vertex w
heads into the polygon as it leaves vertex v. (chordInside)
Added comments for some existing functions.

Flipped drawing to make it "upside-down" from how it used to be. This
has the effect of putting the origin at the bottom-left of the drawing,
and making counter-clockwise polygons look counter-clockwise.