Disabled prop (#74)

* docs(README): add disabled prop usage example

* update Readme

Author: kdastan

README.md

@@ -32,6 +32,46 @@ export default class ExampleComponent extends Component {
 
 The React packager will include the Button component in your app's JS package and make it available for your app to use.
 
+## Disabled prop usage
+
+You can control a button's state by setting `disabled` prop value in this way:
+
+```js
+import React, { Component } from 'react';
+import Button from 'react-native-button';
+
+export default class ExampleComponent extends Component {
+  constructor(props, context) {
+    super(props, context);
+      this.state = {
+        isDisabled: false
+      }
+    }
+  _handlePress() {
+    this.setState({
+      isDisabled: true
+    });
+    console.log('Now, button disabled');
+  }
+  render() {
+    const { isDisabled } = this.state;
+    return (
+      <Button
+        style={{ fontSize: 20, color: 'white' }}
+        styleDisabled={{ color: 'white' }}
+        disabled={isDisabled}
+        containerStyle={{ padding: 10, height: 45, overflow: 'hidden', borderRadius: 4, backgroundColor: 'aqua' }}
+        disabledContainerStyle={{ backgroundColor: 'pink' }}
+        onPress={() => this._handlePress()}
+      >
+        Press Me!
+      </Button>
+    );
+  }
+};
+
+```
+
 ## Container Style
 
 You can make a button with rounded corners like this: