gatsby 0.12.37

Add gatsby-ssr.js for lifecycle APIs during server rendering

on Node.js Yarn

• #695 @mtt87 needed to support rendering translations correctly for his site during the static HTML build so added support for SSR APIs through a new gatsby-ssr.js file which can be added to your site similar to gatsby-browser.js and gatsby-node.js. He added a wrapRootComponent API similar to what was recently added to the browser but the method is now available if we need to add additional SSR APIs.
• @mjesuele added support for extracting data from JS frontmatter when using template literal strings in additional to normal strings in #656

Thanks everyone!