README: add Buildkite + Apache License badge (!238) · Merge requests · Administrator / sourcegraph · GitLab

Administrator requested to merge sg/readme-badges into master Oct 03, 2018

Created by: slimsag

Alternative to https://github.com/sourcegraph/sourcegraph/pull/219

How it looks: https://github.com/sourcegraph/sourcegraph/blob/30c3ed37bafd15839e36756ec8d0fa21d9937b00/README.md

This PR does not need to update the CHANGELOG because it is docs.