Scenegraph benchmark

WIP: This PR adds a benchmark example for comparing scenegraph performance to similar optimal implementations. 

The intent is to add more benchmark examples and optimizations until we get comparable performance (or decide that we will never get comparable performance).
Yes. Firstly, you need to run this test in a context. The error is really that there is no context. Secondly, you need to modify line 182 in `gloo/glir.py`, the `#line 0` must be `#line 2`.