Implementing version tags or releases

[johnctitus]

We ran into an issue when #79 was merged, as troposphere 2.3.1 has a bug in the EC2 CreditSpecification property that caused our templates to fail to build. We were able to pin to the previous commit of jetstream to get back to a lower troposphere version. It did however raise the idea of version tags.

It would be really nice to have versions or releases for this repo, to make pinning to the desired point a little easier and prettier.

[cwgem]

While #89 plus some manual commands gave us this for now, there should be a CircleCI workflow around this. When master gets merged, a specific workflow should probably do the following:

• Look for specific wording in the commit message to indicate a release
• If that exists:
  • Tag the current SHA commit hash (using the Circle environment variable)
  • Push the tag to origin
  • Phase 2: Push a new release to pip so we can have easy installs without relying on git pulldowns

Note that this will most likely depend on getting the Python 3 work sorted out, as pip will deprecate Python 2.7 in the future.