code: function Commit(source, githubClient) {
      this.gh = githubClient;
      this.sha = source.sha;
      this.htmlUrl = source.html_url;
      this.author = source.author;
      this.committer = source.committer;
      this.message = source.message;
      this.treeSha = source.tree.sha;
      this.tree = undefined;
  }
docs: A git commit object. Contains a tree.
  @class Commit
  @param source {Object} JSON response from API, used to build.
  @param githubClient {Object} GitHub API Client object.
  @constructor