Add graphDrawer() function

graphDrawer() "constructor" returns an object with the following members:
- n - number of vertices
- hasEdge(i, j) - return true iff. ij is an edge
- canvas - an HTML 5 canvas object
- position(i) - determine the position of vertex i on the canvas
- timeInterval - time it takes to draw a vertex/edge
- showVertices - display vertices as dots if true
Add completeGraphDrawer() constructor to demonstrate usage of graphDrawer
Add usage comment to graphDrawer