Added Invisible example to README.md

Author: dozoisch

README.md

@@ -35,12 +35,12 @@ function onChange(value) {
 }
 
 render(
-    <ReCAPTCHA
-      ref="recaptcha"
-      sitekey="Your client site key"
-      onChange={onChange}
-    />,
-    document.body
+  <ReCAPTCHA
+    ref="recaptcha"
+    sitekey="Your client site key"
+    onChange={onChange}
+  />,
+  document.body
 );
 ```
 
@@ -57,6 +57,8 @@ Other properties can be used to customised the rendering.
 | tabindex | number | *optional* The tabindex on the element *(__default:__ 0)*
 | onExpired | func | *optional* callback when the challenge is expired and has to be redone by user. By default it will call the onChange with null to signify expired callback. |
 | stoken | string | *optional* set the stoken parameter, which allows the captcha to be used from different domains, see [reCAPTCHA secure-token] |
+| size | enum | *optional* `compact`, `normal` or `invisible`. This allows you to change the size or do an invisible captcha |
+
 
 In order to translate the reCaptcha widget you should create a global variable configuring the desire language, if you don't provide it reCaptcha will pick up the user's interface language.
 
@@ -73,6 +75,39 @@ The component also has some utility functions that can be called.
 - `getValue()` returns the value of the captcha field
 - `reset()` forces reset. See the [JavaScript API doc][js_api]
 
+### Invisible reCAPTCHA
+
+[Invisible reCAPTCHA](https://developers.google.com/recaptcha/docs/versions)
+
+Starting with 0.7.0, the component now supports invisible options. See the [reCAPTCHA documentation](https://developers.google.com/recaptcha/docs/invisible) to see how to configure it.
+
+With the invisible option, you need to handle things a bit differently. You will need to call the execute method by yourself.
+
+```jsx
+var React = require("react");
+var render = require("react-dom").render
+var ReCAPTCHA = require("react-google-recaptcha");
+
+function onChange(value) {
+  console.log("Captcha value:", value);
+}
+
+let captcha;
+
+render(
+  <form onSubmit={() => { captcha.execute(); }}>
+    <ReCAPTCHA
+      ref={(el) => { captcha = el; }}
+      size="invisible"
+      sitekey="Your client site key"
+      onChange={onChange}
+    />
+  </form>,
+  document.body
+);
+```
+
+
 ### Advanced usage
 
 You can also use the barebone components doing the following. Using that component will oblige you to manage the grecaptcha dep and load the script by yourself.
@@ -89,13 +124,13 @@ function onChange(value) {
 }
 
 render(
-    <ReCAPTCHA
-      ref="recaptcha"
-      sitekey="Your client site key"
-      onChange={onChange}
-      grecaptcha={grecaptchaObject}
-    />,
-    document.body
+  <ReCAPTCHA
+    ref="recaptcha"
+    sitekey="Your client site key"
+    onChange={onChange}
+    grecaptcha={grecaptchaObject}
+  />,
+  document.body
 );
 ```