code: function Branch(source, githubClient) {
      this.gh = githubClient;
      this.ref = source.ref;
      this.sha = source.object.sha;
      this.commit = undefined;
  }
docs: Represents a git "reference", but it makes more sense in the context of this
  library to call it a branch. This constructor is not meant to be called
  manually. It is created by the {{#crossLink "GitData"}}{{/crossLink}} object.
  @class Branch
  @param source {Object} JSON response from API, used to build.
  @param githubClient {Object} GitHub API Client object.
  @constructor