update-quilljs.md

Update to latest Quilljs version

1. Change verions number in bower.json to latest version: "quill": "https://github.com/quilljs/quill/releases/download/v1.3.4/quill.tar.gz",
2. Do 'bower update'
3. Compare new styles to old and update
   1. bower_components/quill/quill.bubble.css with polymer-quill-styles-bubble.html
   2. Test bubble and firebase bubble
   3. bower_components/quill/quill.snow.css with polymer-quill-styles-snow.html
   4. Test snow
4. Update package.json with new version number