The Travis CI tests time out on PR builds (see #646 (comment) and #702) and are mostly duplicated by the Azure Pipelines tests, with the following exceptions:

• netcoreapp1.1.2 integration tests
  • Can probably stop running these, since .NET Core 3.0 is now out. netstandard1.3 would be a supported but untested platform. (See Drop support for net461? #636 for possibly removing it.)
• Compression integration tests
  • Are being run on Appveyor (for Windows); probably would be good to test on Azure Pipelines
• Unix Domain Socket tests
  • We don't need to run the full suite of integration tests against Unix sockets (since 99% of the code is the same) but it would be good to add a simple test of opening the connection to the Linux test suites