Convert project to using 'pipenv' to manage dependencies

[javulticat]

Description

Converts the project to use pipenv to manage dependencies, as discussed in Slack.

[coveralls]

Coverage remained the same at 73.292% when pulling 9d54747 on javulticat:jav/pipenv into eda8c48 on zappa:master.

[hellno]

love this! thanks for the PR 💪🏼 much easier to maintain this way (at least to my mind)

I assume you didn't commit the Pipfile.lock on purpose. Is it not needed in this case? (From other projects I'm used to adding it, but that might not be the best way to go 😊)

Basically my question is: are the dependencies fixed enough without having Pipfile.lock?

[javulticat]

love this! thanks for the PR 💪🏼 much easier to maintain this way (at least to my mind)

I assume you didn't commit the Pipfile.lock on purpose. Is it not needed in this case? (From other projects I'm used to adding it, but that might not be the best way to go 😊)

Basically my question is: are the dependencies fixed enough without having Pipfile.lock?

@hellno, I didn't commit Pipfile.lock in this case because the lock file is specific to a single version of Python, whereas Zappa supports Py 3.6 - 3.9. Our options would seem to be either:

1. Commit 1 lock file per version of Python we support
2. Don't commit any lock file, and rely on having dependencies pinned/bounded appropriately in Pipfile (this is the approach I went with as it minimized clutter in the repo)

[hellno]

Love it! The many python versions + less clutter makes a lot of sense 👍🏼