added ability to disable checkbox

src/CheckBox.jsx

@@ -39,6 +39,7 @@ class CheckBox extends React.Component {
             aria-checked={this.state.pressed}
             tabIndex="0"
             onClick={() => this.handleClick()}
+            disabled={props.disabled}
           />
           {props.checkLabel}
         </label>

stories/index.jsx

@@ -134,4 +134,13 @@ storiesOf('CheckBox', module)
       describedBy="checkbox"
       checkLabel="check me out!"
     />
+  ))
+  .add('disabled', () => (
+    <CheckBox
+      name="checkbox"
+      label="CheckBox"
+      describedBy="checkbox"
+      checkLabel="you cannot check me out"
+      disabled="true"
+    />
   ));