Support vue component file that exports Vue.extend. (#95)

* Support vue component file that exports Vue.extend.

Normally, vue component js file exports an options object. For example: export default {props:{title:""}}. In some cases, vue component js file needs to exports Vue.extend. For example: export default Vue.extend(options). Vue natually support it. This fix is used to support Vue.extend when using Vue components in React.

* Fix eslint error.

Fix below two errors:
   3:41  error  Missing space before function parentheses  space-before-function-paren
  16:33  error  Missing space before function parentheses  space-before-function-paren

dist/vuera.cjs.js

@@ -411,7 +411,7 @@ function isReactComponent(component) {
     return false;
   }
 
-  return !(typeof component === 'function' && component.prototype && component.prototype.constructor.super && component.prototype.constructor.super.isVue);
+  return !(typeof component === 'function' && component.prototype && (component.prototype.constructor.super && component.prototype.constructor.super.isVue || component.prototype instanceof Vue));
 }
 
 function isReactForwardReference(component) {

dist/vuera.es.js

@@ -405,7 +405,7 @@ function isReactComponent(component) {
     return false;
   }
 
-  return !(typeof component === 'function' && component.prototype && component.prototype.constructor.super && component.prototype.constructor.super.isVue);
+  return !(typeof component === 'function' && component.prototype && (component.prototype.constructor.super && component.prototype.constructor.super.isVue || component.prototype instanceof Vue));
 }
 
 function isReactForwardReference(component) {

dist/vuera.iife.js

@@ -408,7 +408,7 @@ function isReactComponent(component) {
     return false;
   }
 
-  return !(typeof component === 'function' && component.prototype && component.prototype.constructor.super && component.prototype.constructor.super.isVue);
+  return !(typeof component === 'function' && component.prototype && (component.prototype.constructor.super && component.prototype.constructor.super.isVue || component.prototype instanceof Vue));
 }
 
 function isReactForwardReference(component) {

src/utils/isReactComponent.js

@@ -1,3 +1,5 @@
+import Vue from 'vue'
+
 export default function isReactComponent (component) {
   if (typeof component === 'object' && !isReactForwardReference(component)) {
     return false
@@ -6,8 +8,8 @@ export default function isReactComponent (component) {
   return !(
     typeof component === 'function' &&
     component.prototype &&
-    component.prototype.constructor.super &&
-    component.prototype.constructor.super.isVue
+    ((component.prototype.constructor.super && component.prototype.constructor.super.isVue) ||
+      component.prototype instanceof Vue)
   )
 }