confirmation modal for deleting an application

- adds delete-confirmation Vue component
- refactors some button styles to make them globally available

js/components/delete_confirmation.js

@@ -0,0 +1,15 @@
+export default {
+  name: 'delete-confirmation',
+
+  data: function() {
+    return {
+      deleteText: '',
+    }
+  },
+
+  computed: {
+    valid: function() {
+      return this.deleteText.toLowerCase() === 'delete'
+    },
+  },
+}