Building for python 3.6

[spockNinja]

This project looks awesome. We are currently using Zappa, but aren't satisfied with it's bloat or packaging behavior.

One big thing missing for us is the ability to package a python 3.6 lambda application.

I believe it would be a pretty simple addition, but want to make sure it would be a welcome PR, and that my approach would be acceptable.

The only two changes I had to make locally were:

https://github.com/NoRedInk/make-lambda-package/blob/master/make_lambda_package/deps.py#L58

and

https://github.com/NoRedInk/make-lambda-package/blob/master/make_lambda_package/archive.py#L36

The rest seemed to work just fine. So I think it would be safe to put the python version behind another cli argument that defaults to 'python2.7' and also allows 'python3.6'. That argument could then be passed to build_deps and make_archive.

If a PR with that approach would be welcome, I would be happy to whip it up. Thanks!

[ento]

Thanks for reaching out! The approach sounds good to me.

--runtime might be a fitting name for the flag, though I'll leave it up to you :)

[spockNinja]

Awesome! --runtime sounds perfect. I'll try to get that whipped up in short order.