added zoom and zoomBy call forward to svg-pan-zoom api

src/SvgPanZoom.vue

@@ -23,9 +23,11 @@ import { EventBus } from './EventBus';
 
 import SvgPanZoomThumbnail from './SvgPanZoomThumbnail.vue';
 
+import { SvgPanZoomApi } from './SvgPanZoomApi';
+
 export default {
-    props,
   components: { SvgPanZoomThumbnail },
+  props,
   computed: {
     has_thumbnail: function() { return this.$slots.thumbnail },
     options: function() {
@@ -40,6 +42,10 @@ export default {
       return options;
     }
   },
+  data: () => ({
+    spz: null,
+    bus: EventBus()
+  }),
   mounted: function() {
     let options = {};
 
@@ -59,7 +65,14 @@ export default {
 
     this.$emit( 'svgpanzoom', this.spz );
   },
-    data: () => ({ spz: null, bus: EventBus() }),
+  methods: {
+    zoom: function( v ){
+      this.spz.zoom( v );
+    },
+    zoomBy: function( v ){
+      this.spz.zoomBy( v );
+    }
+  }
 };
 
 </script>

src/SvgPanZoomApi.js

@@ -0,0 +1,6 @@
+export const SvgPanZoomApi = ( SvgPanZoomInstance ) => ({
+  zoom: function( v ){
+    SvgPanZoomInstance.zoom( v );
+  },
+  zoomBy: ( v ) => SvgPanZoomInstance.zoomBy( v )
+});