fixes issue with usage example

* converted to single-quotes (vue-cli default)
* added `Vue` import
* added `vfg.css` import
* fixed spacing
* fixed `formOptions` (was inside of `schema`)
* added `validateAsync` to `formOptions`

Author: zoul0813

usage.md

@@ -15,99 +15,101 @@ This is a simple usage example:
 ```
 
 ```js
-import VueFormGenerator from "vue-form-generator";
+import Vue from 'vue'
+import VueFormGenerator from 'vue-form-generator'
+import 'vue-form-generator/dist/vfg.css'
 
-Vue.use(VueFormGenerator);
+Vue.use(VueFormGenerator)
 
-/* optional custom validators treated as "built-in"
+/* optional custom validators treated as 'built-in'
 Vue.use(VueFormGenerator, {
-  validators: objectWithCustomValidatorFunctions  
+  validators: objectWithCustomValidatorFunctions
 });
 */
 
 export default {
   data () {
     return {
-      
+
       model: {
         id: 1,
-        name: "John Doe",
-        password: "J0hnD03!x4",
-        skills: ["Javascript", "VueJS"],
-        email: "[email protected]",
+        name: 'John Doe',
+        password: 'J0hnD03!x4',
+        skills: ['Javascript', 'VueJS'],
+        email: '[email protected]',
         status: true
       },
-      
+
       schema: {
         groups: [
           {
-            legend: "User Details",
+            legend: 'User Details',
             fields: [
               {
-                type: "input",
-                inputType: "text",
-                label: "ID (disabled text field)",
-                model: "id",
+                type: 'input',
+                inputType: 'text',
+                label: 'ID (disabled text field)',
+                model: 'id',
                 readonly: true,
                 disabled: true
               },
               {
-                type: "input",
-                inputType: "text",
-                label: "Name",
-                model: "name",
-                id: "user_name",
-                placeholder: "Your name",
+                type: 'input',
+                inputType: 'text',
+                label: 'Name',
+                model: 'name',
+                id: 'user_name',
+                placeholder: 'Your name',
                 featured: true,
                 required: true
               },
               {
-                type: "input",
-                inputType: "email",
-                label: "E-mail",
-                model: "email",
-                placeholder: "User's e-mail address"
+                type: 'input',
+                inputType: 'email',
+                label: 'E-mail',
+                model: 'email',
+                placeholder: 'User\'s e-mail address'
               },
               {
-                type: "input",
-                inputType: "password",
-                label: "Password",
-                model: "password",
+                type: 'input',
+                inputType: 'password',
+                label: 'Password',
+                model: 'password',
                 min: 6,
                 required: true,
-                hint: "Minimum 6 characters",
-                validator: validators.string
+                hint: 'Minimum 6 characters',
+                validator: 'string'
               }
             ]
           },
           {
-            legend: "Skills & Status",
+            legend: 'Skills & Status',
             fields: [
               {
-                type: "select",
-                label: "skills",
-                model: "type",
-                values: ["Javascript", "VueJS", "CSS3", "HTML5"]
+                type: 'select',
+                label: 'skills',
+                model: 'type',
+                values: ['Javascript', 'VueJS', 'CSS3', 'HTML5']
               },
               {
-                type: "checkbox",
-                label: "Status",
-                model: "status",
+                type: 'checkbox',
+                label: 'Status',
+                model: 'status',
                 default: true
               }
             ]
           }
-          ],
-          
-          formOptions: {
-            validateAfterLoad: true,
-            validateAfterChanged: true,
-            fieldIdPrefix: 'user-'
-          }
-        }
+        ]
+      },
+
+      formOptions: {
+        validateAfterLoad: true,
+        validateAfterChanged: true,
+        fieldIdPrefix: 'user-'
       }
     }
   }
+}
 ```
 ```html
 </script>