Run benchmarks on Travis

[asmeurer]

We should figure out how to run the benchmarks on Travis to make sure they work (not to check for performance regressions).

[peytondmurray]

Now that Travis is not being used, I propose removing Travis configuration entirely and looking into using Github actions for this. We could run benchmarks on new PRs as part of CI - https://github.com/ionelmc/pytest-benchmark/ and https://github.com/benchmark-action/github-action-benchmark may be of help here. I could begin looking into this by spending <10 hours on it for an initial attempt.