In case you haven't heard of it, you might want to take a look at LeanPub, who specialize in books that are published while they are being written, have a particular focus on Software Development books, and accept manuscripts written in Markdown stored in a Dropbox folder. You can then take the finished LeanPub book to a print-on-demand company like Lulu or CreateSpace to created printed books as well:

  https://leanpub.com/authors

I actually assumed you were making a LeanPub book, and was considering buying the work in progress.

Thank you for building this. As weird as it sounds saying this out loud, you've made the world slightly better.