Update README with better code snippet formatting

Author: cooperka

README.md

@@ -1,60 +1,59 @@
 # react-native-snackbar
 
-Implementation of the material design Snackbar component for both Android and iOS. See [Google Design](https://material.google.com/components/snackbars-toasts.html) for more info.
+Implementation of the material design Snackbar component for both Android and iOS.
+See [Google Design](https://material.google.com/components/snackbars-toasts.html) for more info.
 
 ## Installation
 
 To use this extension, you have to do the following steps:
 
 1. In your react-native project, run
 
-	- using npm
+    - using npm:
 
-      	```
-    	npm install react-native-snackbar
-    	```
+        ```shell
+        npm install react-native-snackbar
+        ```
 
-	- using yarn:
+    - using yarn:
 
-    	```
-    	yarn add react-native-snackbar
-    	```
+        ```shell
+        yarn add react-native-snackbar
+        ```
 
-2. Link the library using `react-native link react-native-snackbar` (learn more about [linking](https://facebook.github.io/react-native/docs/linking-libraries-ios.html).
+2. Link the library using `react-native link react-native-snackbar`
+(learn more about [linking](https://facebook.github.io/react-native/docs/linking-libraries-ios.html).
 
-3. Import it in you JS, where you want to show a snackbar
-	```
-	import Snackbar from 'react-native-snackbar';
-	```
+3. Import it in your JS where you want to show a snackbar:
+
+    ```js
+    import Snackbar from 'react-native-snackbar';
+    ```
 
 ## Usage
 
-To show a simple snackbar simply call:
-```
+To show a simple snackbar:
+
+```js
 Snackbar.show({
-	title: 'Hello world',
+    title: 'Hello world',
 
-	// Optional duration. Can be one of LENGTH_LONG | LENGTH_SHORT | LENGTH_INDEFINITE.
-	duration: Snackbar.LENGTH_LONG,
+    // Optional duration. Can be one of LENGTH_LONG | LENGTH_SHORT | LENGTH_INDEFINITE.
+    duration: Snackbar.LENGTH_LONG,
 });
 ```
 
-*..Preview..*
+Or, to include an action button:
 
-To add an action:
-```
+```js
 Snackbar.show({
-	title: 'Hello world',
-	action: {
-		title: 'UNDO',
-		color: 'green',
-		onPress: () => {
-			// do something here
-		},
-	},
+    title: 'Hello world',
+    action: {
+        title: 'UNDO',
+        color: 'green',
+        onPress: () => { /* Do something. */ },
+    },
 });
 ```
 
-Note that actions do not currently work on Android. Feel free to submit a PR!
-
-*..Preview..*
+TODO: Add screenshots :sunglasses: