Create helpers

[Oyanel]

Hello,

First nice work, your module is really useful ! I use it in a node app to expose it to different front-end apps though an API.

To get a manga related information, you need to send a Manga object. I think it would be useful to create an helper(kind of getMangaById()) to get a Manga object with just its Id. The purpose is to save just an Id and not a whole Manga object in my app.

It's just an idea, if you think it's usefull I'll contrib.