* Added support for GitHub bearer token
* Added support for GitHub bearer token

GitHub's API will rate limit unauthenticated requests from IPs with high request
rates, but will allow requests that include authentication. This adds
support for reading in a `GITHUB_TOKEN` environment variable and adding
it as a bearer token to requests against the GitHub API

kubernetes/perf-tests,kubernetes/perf-tests,kubernetes/perf-tests,shyamjvs/perf-tests,shyamjvs/perf-tests,kubernetes/perf-tests,kubernetes/perf-tests,shyamjvs/perf-tests,shyamjvs/perf-tests,shyamjvs/perf-tests