Add remove attachment button

src/components/post_status_form/post_status_form.js

src/components/post_status_form/post_status_form.vue

static/font/config.json

static/font/css/fontello-codes.css

static/font/css/fontello-embedded.css

static/font/css/fontello-ie7-codes.css

static/font/css/fontello-ie7.css

static/font/css/fontello.css

static/font/demo.html

static/font/font/fontello.eot

static/font/font/fontello.svg

static/font/font/fontello.ttf

static/font/font/fontello.woff

static/font/font/fontello.woff2