Updates to readme and packages

[code247]

This PR addresses following tasks:

• tidy up README to list runtime images and move long tutorial to a separate file.
• update python package versions.
• pull common packages to requirements_common.txt and reuse it across runtimes.

[code247]

@rabbah Can you add yourself / other relevant reviewers? Thank you!

[sciabarracom]

I do not think we can update package versions in existing runtimes because this would break compatibility. Usually you do newer versions of libraries in runtimes for newer versions of languages but leave the verions of packages in older runtimes. If you want newer versions of a package for an action you can always use a virtual env. I personally did an update of versions of runtimes and I was told to revert to older version of packages

[rabbah]

Updating the versions of existing packages is OK. Vendors are more cognizant of these updates but we can keep things up to date.

There are some things in the README that should be updated (for example, we remove the "loop" from "actionloop") but since those exist in the current docs, we can fix this subsequent to the refactoring.

Thanks @sciabarracom for the review and thanks @code247 for the contribution 🎉 Do you have a CLA on file with Apache, I could not find one.

[rabbah]

Not sure what's going on with Travis. @code247 are you rebased to master?

[code247]

@rabbah Addressed your comments. I'm not quite sure about invoke.py. Just fyi, I haven't added the local build tutorial but rather just moved it from main README given it seemed verbose to be there. Happy to clean it up though! 🙂

Regarding CI, I have rebased my branch with master but not sure why it is not kicking off.

[sciabarracom]

The invoke.py is here and its use is straightfoward: python3 invoke.py init <file> and python3 invoke.py run '<json>'. It is equivalent to almost all the curl you wrote but simpler to use.

[rabbah]

@dgrove-oss can we disable the travis check on PRs? There's an issue with Travis reporting max users/seats exhausted. I'm going to try to run the Travis job as a GHA.

[dgrove-oss]

We can change the required checks by editing .asf.yaml.

[dgrove-oss]

fwiw, the last travis run on this PR failed because of a missing license header, not a max user problem

[rabbah]

Thanks @dgrove-oss - the travis link wasn't showing me the build. Of course, I should've gone to Travis' dashboard directly.

the previous build: https://app.travis-ci.com/github/apache/openwhisk-runtime-python/builds/238685042 the current build: https://app.travis-ci.com/github/apache/openwhisk-runtime-python/builds/239149380

[dgrove-oss]

yeah, its on my back burner list to go through all of the readme.md files and add /github to the travis url piece like I did here: https://github.com/apache/openwhisk-runtime-docker/commit/4f85c3924663ba871af672d3cfe35efcf31f0e20

[rabbah]

thanks @code247 🎉