Refresh figures with minor fixes to plot script

[jvlmdr]

The scipy solver is now considerably faster, although lapsolver still has an advantage for small problems. I have updated the benchmarks to reflect this.

See the figures here: https://github.com/jvlmdr/py-lapsolver/blob/5f0c0d830fda6829dd1f7f38aa6ad25e5f18f297/ReadMe.md

[cheind]

Thanks Jack!