I tried to add a benchmark test for suspendable binding but ended up with cyclical dependencies trying to have kotlin-result jvmBenchmark source set depend on kotlin-result-coroutine project (which already depends on kotlin-result).

Would make life a lot easier to just move benchmarking to its own subproject. It would also simplify the current kotlin-result gradle file which has a bunch

Add steps to run unit tests on python 3.7, and python 3.8 in the tox.ini file, and in the travis build.