Check runtime benchmark values

[AlexLipp]

Currently the runtime benchmarking script indicates that the SCS solver is three orders of magnitude faster than ECOS and GUROBI. This is highly improbable and likely indicates a problem with the benchmarking. A possibility is a conversion from ms to seconds somewhere in the processing chain.

• The source of the discrepancy in runt-times needs to be isolated.
• If the error comes from CVXPY reporting run-times in ms not seconds, an issue ought be raised as this is contrary to the documentation.
• Else, the run-time reporting in funmixer needs to be fixed.

[AlexLipp]

This error may simply be due to a manual scaling factor in the plotting section of runtime_benchmark.py. This figure shows the results of the scaling factor of 1e-3 being removed from the SCS plotting commands. Now the runtimes are comparable in time in accordance with other tests.