Add VC traffic (Python) and Hughes' model solvers

[GitKalo]

Recently I worked on a project to implement Hughes' pedestrian model in 1D via Clawpack. In the process, I also created a solver for VC traffic written in Python (since currently as far as I can tell only a Fortran version is available.

[ketch]

Thanks, this looks very interesting! We like to make sure that all Riemann solvers have examples that can be used to test them -- do you have a script to set up and run an example with each of these solvers? Those could be contributed to pyclaw/examples or the apps module.

There are in fact two existing Riemann solvers for variable-coefficient traffic flow, so it might be interesting to compare with them:

https://github.com/clawpack/riemann/blob/master/src/rp1_traffic_vc.f90 https://github.com/clawpack/riemann/blob/master/src/rp1_traffic_vc_fwave.f90