Added font-awesome buttons for comment icon

frontend/index.html

...d/src/components/submission_notes/AnnotatedSubmission.vue

frontend/static/font-awesome-4.7.0/HELP-US-OUT.txt

frontend/static/font-awesome-4.7.0/css/font-awesome.css

frontend/static/font-awesome-4.7.0/css/font-awesome.min.css

frontend/static/font-awesome-4.7.0/fonts/FontAwesome.otf

...d/static/font-awesome-4.7.0/fonts/fontawesome-webfont.eot

...d/static/font-awesome-4.7.0/fonts/fontawesome-webfont.svg

...d/static/font-awesome-4.7.0/fonts/fontawesome-webfont.ttf

.../static/font-awesome-4.7.0/fonts/fontawesome-webfont.woff

...static/font-awesome-4.7.0/fonts/fontawesome-webfont.woff2

frontend/static/font-awesome-4.7.0/less/animated.less

frontend/static/font-awesome-4.7.0/less/bordered-pulled.less

frontend/static/font-awesome-4.7.0/less/core.less

frontend/static/font-awesome-4.7.0/less/fixed-width.less

frontend/static/font-awesome-4.7.0/less/font-awesome.less

frontend/static/font-awesome-4.7.0/less/icons.less

frontend/static/font-awesome-4.7.0/less/larger.less

frontend/static/font-awesome-4.7.0/less/list.less

frontend/static/font-awesome-4.7.0/less/mixins.less