Updated code to use latest buefy version

Author: Peter Samoilov

pystacker-front/src/components/Stack/Card.vue

@@ -140,7 +140,7 @@
           })
       },
       del() {
-        this.$dialog.confirm({
+        this.$buefy.dialog.confirm({
           title: 'Deleting stack',
           message: 'Are you sure you want to <b>delete</b> stack? This action cannot be undone.',
           confirmText: 'Delete stack',

pystacker-front/src/components/Stack/Create.vue

@@ -69,7 +69,7 @@
       createAndLeave() {
         this.$store.dispatch('stacks/createStack', {id: this.id, vars: this.collectVars(), name: this.name})
           .then((r) => this.$router.push("/stack/" + r['id']))
-          .catch(r => this.$toast.open({
+          .catch(r => this.$buefy.toast.open({
             duration: 5000,
             message: `Error creating stack: ${r}`,
             position: 'is-top',

pystacker-front/src/components/Stack/ViewStack.vue

@@ -177,7 +177,7 @@
                     })
             },
             del() {
-                this.$dialog.confirm({
+                this.$buefy.dialog.confirm({
                     title: 'Deleting stack',
                     message: 'Are you sure you want to <b>delete</b> stack? This action cannot be undone.',
                     confirmText: 'Delete stack',