moved mentions into a separate component - MentionLine, added collapsing

of mentions when there's too many of 'em

src/components/mentions_line/mentions_line.js

@@ -0,0 +1,51 @@
+import MentionLink from 'src/components/mention_link/mention_link.vue'
+import { mapGetters } from 'vuex'
+
+const MentionsLine = {
+  name: 'MentionsLine',
+  props: {
+    attentions: {
+      required: true,
+      type: Object
+    }
+  },
+  data: () => ({ expanded: false }),
+  components: {
+    MentionLink
+  },
+  computed: {
+    oldStyle () {
+      return this.mergedConfig.mentionsOldStyle
+    },
+    limit () {
+      return 1
+    },
+    mentions () {
+      return this.attentions.slice(0, this.limit)
+    },
+    extraMentions () {
+      return this.attentions.slice(this.limit)
+    },
+    manyMentions () {
+      return this.extraMentions.length > 0
+    },
+    buttonClasses () {
+      return [
+        this.oldStyle
+          ? 'button-unstyled'
+          : 'button-default -sublime',
+        this.oldStyle
+          ? '-oldStyle'
+          : '-newStyle'
+      ]
+    },
+    ...mapGetters(['mergedConfig']),
+  },
+  methods: {
+    toggleShowMore () {
+      this.expanded = !this.expanded
+    }
+  }
+}
+
+export default MentionsLine