createComment method
Creates a comment for a gist.
API docs: https://developer.github.com/v3/gists/comments/#create-a-comment
Implementation
Future<GistComment> createComment(String gistId, CreateGistComment request) {
return github.postJSON('/gists/$gistId/comments',
body: GitHubJson.encode(request),
convert: (dynamic i) => GistComment.fromJson(i));
}