Leverage OkHttpConnector

[justinharringa]

When we send pull requests, we will see the following message and it's possible that this may stop working eventually. Reference: hub4j/github-api#754

[main] INFO com.salesforce.dockerfileimageupdate.subcommands.impl.Parent - Fixing Dockerfiles in dockerfile-image-update/somecontainers to PR to justinharringa/somecontainers
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.kohsuke.github.GitHubHttpUrlConnectionClient$HttpURLConnectionResponseInfo (file:/Users/jharringa/ws/dockerfile-image-update/dockerfile-image-update/target/dockerfile-image-update-1.0-SNAPSHOT.jar) to field java.net.HttpURLConnection.method
WARNING: Please consider reporting this to the maintainers of org.kohsuke.github.GitHubHttpUrlConnectionClient$HttpURLConnectionResponseInfo
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release