fix(if-core.js): child view re-binding issue

sets showing to false on unbind to ensure binding is carried out when view is re-shown
nested views were not re-bound when parent was re-shown

Resolves
#317
#315

dist/amd/if-core.js

@@ -33,6 +33,7 @@ define(["exports"], function (exports) {
       this.view.unbind();
 
       if (!this.viewFactory.isCaching) {
+        this.showing = false;
         return;
       }
 

dist/commonjs/if-core.js

@@ -32,6 +32,7 @@ var IfCore = exports.IfCore = function () {
     this.view.unbind();
 
     if (!this.viewFactory.isCaching) {
+      this.showing = false;
       return;
     }
 

dist/es2015/if-core.js

@@ -23,6 +23,7 @@ export let IfCore = class IfCore {
     this.view.unbind();
 
     if (!this.viewFactory.isCaching) {
+      this.showing = false;
       return;
     }
 

dist/native-modules/if-core.js

@@ -26,6 +26,7 @@ export var IfCore = function () {
     this.view.unbind();
 
     if (!this.viewFactory.isCaching) {
+      this.showing = false;
       return;
     }
 

dist/system/if-core.js

@@ -36,6 +36,7 @@ System.register([], function (_export, _context) {
           this.view.unbind();
 
           if (!this.viewFactory.isCaching) {
+            this.showing = false;
             return;
           }
 

dist/temp/aurelia-templating-resources.js

@@ -420,6 +420,7 @@ var IfCore = exports.IfCore = function () {
     this.view.unbind();
 
     if (!this.viewFactory.isCaching) {
+      this.showing = false;
       return;
     }
 

src/if-core.js

@@ -31,6 +31,7 @@ export class IfCore {
     // For example a view could be returned to the cache and reused while it's still
     // attached to the DOM and animated.
     if (!this.viewFactory.isCaching) {
+      this.showing = false;
       return;
     }