added some new key bindings
added lighting and 2D surfaces
show more warnings
added key to toggle lighting
turn it into a library
improved Makefile
turn the *_step variables into const options
fixed bug with global pendulum instance
make the graph pointer function stuff easier to read
fix window title
added support for multiple graphs
added comment about global pendulum instance
allow specifying number of dimensions for a graph
added keys to disable graphs, polishing
implement vector fields
improve drawing algos
added support for particles