Add compatibility test for v1.2.0

[chenrui333]

Description

Fixes #880

Update build config for Bazel 1.1.0 and Bazel 1.2.0

Motivation

Keep up to date with the latest Bazel and meetup is actually actively using this lib.

[chenrui333]

Right now we are actually using Bazel 1.1.0 in production, so I am confident with Bazel 1.1.0 upgrade.

But it would be nice to also introduce the compatibility test for Bazel 1.2.0 as well. :)

[chenrui333]

Also relates to chenrui333/rules_openapi#22

[ittaiz]

Thanks!
I’d rather we update 1.0.0 to 1.2.0 since our past experience tells us that having too many versions on Travis kills our ability to merge code in easily.

[chenrui333]

@ittaiz Sounds totally reasonable. Let me update it.

[ittaiz]

LGTM, thanks!

[ittaiz]

build failed. Can you PTAL?

[ittaiz]

We can have two PRs by the way. We can have to upgrade to 1.1.0 and then a followup one to replace it with 1.2.0
If we do that I'd appreciate the diffs to be as small as possible (should be close to replacing 1.0.0 to 1.1.0 and so on)

[chenrui333]

Sure. Sounds like a better idea.

[chenrui333]

Breakdown the upgrade steps in new PRs, closing this one for now :)