Fix Changelog formatting
Fix Changelog formatting

The different heading levels are causing issues for services that are trying to read and filter the changelog
mixonic/ember.js,mixonic/ember.js,sly7-7/ember.js,knownasilya/ember.js,knownasilya/ember.js,elwayman02/ember.js,tildeio/ember.js,stefanpenner/ember.js,elwayman02/ember.js,elwayman02/ember.js,sly7-7/ember.js,knownasilya/ember.js,tildeio/ember.js,elwayman02/ember.js,emberjs/ember.js,mixonic/ember.js,emberjs/ember.js,tildeio/ember.js,stefanpenner/ember.js,stefanpenner/ember.js,emberjs/ember.js,sly7-7/ember.js