Update readme to show promise usage

Author: joeferraro

README.md

@@ -4,14 +4,15 @@ Cookie manager for react native.
 
 ### Installation
 
-1. `npm install react-native-cookies`
-2. `rnpm link react-native-cookies` - (run `npm install -g rnpm` if required)
-3. Om nom nom nom cookies.
+```
+yarn add react-native-cookies
+react-native link react-native-cookies
+```
 
 ### Usage
 
 ```javascript
-var CookieManager = require('react-native-cookies');
+import CookieManager from 'react-native-cookies';
 
 // set a cookie (IOS ONLY)
 CookieManager.set({
@@ -22,7 +23,7 @@ CookieManager.set({
   path: '/',
   version: '1',
   expiration: '2015-05-30T12:30:00.00-05:00'
-}, (err, res) => {
+}).then((res) => {
   console.log('cookie set!');
   console.log(err);
   console.log(res);
@@ -31,37 +32,37 @@ CookieManager.set({
 // Set cookies from a response header
 // This allows you to put the full string provided by a server's Set-Cookie 
 // response header directly into the cookie store.
-CookieManager.setFromResponse('http://example.com', 'user_session=abcdefg; path=/; expires=Thu, 1 Jan 2030 00:00:00 -0000; secure; HttpOnly', (res) => {
-  // `res` will be true or false depending on success.
-  console.log("Set cookie", res);
-})
+CookieManager.setFromResponse(
+  'http://example.com', 
+  'user_session=abcdefg; path=/; expires=Thu, 1 Jan 2030 00:00:00 -0000; secure; HttpOnly')
+    .then((res) => {
+      // `res` will be true or false depending on success.
+      console.log('set cookie result', res);
+    });
 
 // Get cookies as a request header string
-CookieManager.get('http://example.com', (err, res) => {
-  console.log('Got cookies for url', res);
-  // Outputs 'user_session=abcdefg; path=/;'
-})
+CookieManager.get('http://example.com')
+  .then((res) => {
+    console.log('cookies for url', res); // => 'user_session=abcdefg; path=/;'
+  });
 
 // list cookies (IOS ONLY)
-CookieManager.getAll((err, res) => {
-  console.log('cookies!');
-  console.log(err);
-  console.log(res);
-});
+CookieManager.getAll()
+  .then(res) => {
+    console.log('all cookies', res);
+  });
 
 // clear cookies
-CookieManager.clearAll((err, res) => {
-  console.log('cookies cleared!');
-  console.log(err);
-  console.log(res);
-});
+CookieManager.clearAll()
+  .then(res) => {
+    console.log('cookies cleared', res);
+  });
 
 // clear a specific cookie by its name (IOS ONLY)
-CookieManager.clearByName('cookie_name', (err, res) => {
-  console.log('cookie cleared!');
-  console.log(err);
-  console.log(res);
-});
+CookieManager.clearByName('cookie_name')
+  .then(res) => {
+    console.log('cookie cleared', res);
+  });
 
 ```