Add the ability to have a metadata file created for the chapter/all chapters

[saxx0n]

As part of my workflow I take the downloaded chapters and insert a ComicInfo.xml into the cbz files. However, right now this step has to be manually generated and requires a bunch of work for things like dates a chapter was released. It would be awesome if some or all of that information could be generated since it should all be available on the site.

Something like adding a "--metadata" flag, to create a file with author, and date for each chapter.