Update CHANGELOG

CHANGELOG.md

@@ -20,6 +20,8 @@ key. Any code referencing `node.type` and others will need changed to
 - Changed the id for the root `<div>` used by Gatsby to mount React to `___gatsby`
 - The default layout component should be at `layouts/index.js` not `layouts/default.js` https://github.com/gatsbyjs/gatsby/pull/940#issuecomment-300537162
 - `this.props.children` in layout components is now a *function* https://github.com/gatsbyjs/gatsby/pull/940#issuecomment-300878300
+- Change the default port for serve-build to 9000
+- Change the path to GraphiQL to `/___graphql`
 
 ### Chore
 - Upgrade Jest to v20 #935