Add a Dockerfile to allow running from a container

[slim-bean]

I took the approach here of making the Dockerfile "interactive", if you run it in an interactive way you can manually run the speedtest command, this can be happy if you are trying to troubleshoot something from within a containerized environment.

I also included examples of how you would run the Dockerfile in a non-interactive way if you just want to run the command without installing it on your machine.

Lastly a included a few Kubernetes examples of how you might deploy this to run it from a Kubernetes environment

I also updated Go.

[r3inbowari]

Thank you! I left a comment.

[melroy89]

I think this is still a very good PR.

[r3inbowari]

@melroy89 thanks a lot! @slim-bean