Postprocessing of test results

[mabelzhang]

Postprocessing scripts should be created to read the test result logs from #24, plot the results to compare different test cases, different simulators, etc.

In order to compare results across different simulators, the postprocessing scripts should be simulator-independent. This should be satisfied as long as the log format is simulator-independent, and all simulators output the same format, to be processed by the same postprocessing script(s).

Usage, inputs, and outputs of the scripts should be documented.

Starting point: see existing plots in https://github.com/scpeters/benchmark/tree/master/pdf