Move graph creation to the client

[tobami]

There are some graph-related issues (#24, #39) that, while solvable, would just go away if the rendering was done by the client. It would also be faster because the image would not need to be loaded from the server.

There is no mature Javascript Graphviz library. The most promising JS graph library is D3, but it has no implementation of the graphviz algorithm, but there has been some discussion surrounding it.

Issue d3/d3#349 has been created, so we watch it and when it is implemented we can move rendering to the client.