Add gRPC 1.4 and Python 3.6 support

[davidgasquez]

This PR is related to https://github.com/grpc/grpc-docker-library/issues/45. The new 1.4 folder contains a Dockerfile that implements gRPC 1.4 for Python 3.6.

Happy to change anything! Let me know your thoughts and feedback 😄

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[davidgasquez]

I signed it!

[googlebot]

CLAs look good, thanks!

[nathanielmanistaatgoogle]

Please squash commits and conform to these commit message guidelines.

I'd forgotten this repository existed! What brings you here? Thanks for the improvement!

[davidgasquez]

Commits squashed @nathanielmanistaatgoogle! Let me know if I should do anything else :)

We've started to use gRPC and instead of building our own base image I decided to contribute here. 😄

[nathanielmanistaatgoogle]

Whoops; something else I forgot: we recently relicensed, so I don't think it's appropriate to copy the license headers off the extant files in this repository. See this file for the license header that (I believe) should be used for new files.

[davidgasquez]

Thanks for the information @nathanielmanistaatgoogle! 😄 I updated the License on both Dockerfiles.

[nathanielmanistaatgoogle]

Thanks!

[davidgasquez]

Sorry @nathanielmanistaatgoogle, do you know if the new images will be available in https://hub.docker.com/r/grpc/python/builds/?

[markmandel]

I can set that up - at an event at the moment, but will jump on it today/tomorrow. Feel free to harass me if need be. 👍

[markmandel]

New images are now live!

[davidgasquez]

Thanks for setting that up @markmandel! Also, thanks again @nathanielmanistaatgoogle for the help. 😄