Build manylinux wheels

[movermeyer]

Use manylinux to build wheels for all the major linux distributions, for both x86_64 and i686 architectures.

First step towards #25

---

@thomasst: Check it out! 😁

Create the release artifacts

Send a POST request to the CircleCI API to trigger the build_wheels workflow.

Substitute $CIRCLE_TOKEN with your personal API token:

curl --location --request POST 'https://circleci.com/api/v2/project/gh/closeio/ciso8601/pipeline' \
--header 'Circle-Token: $CIRCLE_TOKEN' \
--header 'Content-Type: application/json' \
--data-raw '{
  "branch": "mo.build_wheels",
  "parameters": {
    "build_wheels": true
  }
}'

[thomasst]

Instead of having to do this manually, could we use a commit tag, e.g. specifying the string #buildwheels in the commit message would trigger the wheels?

[movermeyer]

Good point.

We should sort out the release process.

[movermeyer]

We should not merge this until we have confirmed that the pre-built wheels are not super slow relative to the "compiled from the sdist" ones.

If there is a discrepancy, we should include instructions in the README for how to force pip to use the source distribution instead of the pre-built wheels.

[movermeyer]

Closing in favour of #97