[Work in Progress] Python SDK

[lyndsysimon]

I've had some free time in the past few days, and have gotten far enough along in throwing together a Python SDK for Pipedream that I thought it might be worthwhile to go ahead and push it back to you. NOTE: This branch is subject to rebasing, so please don't build directly on top of it. I will rebase it upon the most recent changes once I'm at a stable and reasonably feature-complete stage and note here when I feel it's ready for inclusion into the mainline branch.

As it stands, the library can successfully send an unsigned event to the API, and that event does in fact show up in the web UI for the workflow.

It lacks proper error handling, and I don't have an API secret yet to verify that the signature I'm generating for the header will validate. I've also not yet ensured that values other than the raw_event are properly handled.

Finally, there is code cleanup to do and more infrastructure work - ensuring compatibility with various Python versions, enforcing PEP8 compliance, integrating the tests (oh, and writing those...) with CircleCI, and getting the package submitted to PyPI.

I'll keep hacking at it as time allows, I just wanted to make sure the team had visibility into the progress I've made thus far.