Move documentation to its own site

[nozzlegear]

ShopifySharp now has too many services to keep all documentation in one single readme file. I'd like to move the documentation to either GitHub pages or a site of my own. Docs will live in a doc folder and the site will pull the documentation from there. While the GitHub wiki might work, for business reasons I'd like to put the documentation on a site where I can use MailChimp forms. 😉

No ETA on this right now.