plugin doc tweaks

README.md

@@ -1235,19 +1235,20 @@ Then:
 
 ## Plugins
 
-Plugins should be registered with reveal.js by calling `Reveal.registerPlugin( 'myPluginID', MyPlugin )`. Registered plugin instances should expose an "init" function that reveal.js can call to initialize them.
+Plugins should register themselves with reveal.js by calling `Reveal.registerPlugin( 'myPluginID', MyPlugin )`. Registered plugin instances can optionally expose an "init" function that reveal.js will call to initialize them.
 
-When reveal.js is booted up via `Reveal.initialize()`, it will go through all registered plugins and invoke their "init" methods. If the "init" method returns a Promise, reveal.js will wait for that promise to be fullfilled before finshing the startup sequence and firing the [ready](#ready-event) event. Here's an example of a plugin that returns a promise:
+When reveal.js is booted up via `Reveal.initialize()`, it will go through all registered plugins and invoke their "init" methods. If the "init" method returns a Promise, reveal.js will wait for that promise to be fullfilled before finshing the startup sequence and firing the [ready](#ready-event) event. Here's an example of a plugin that does some asynchronous work before reveal.js can proceed:
 
 ```javascript
-Reveal.registerPlugin( 'myPlugin', {
+let MyPlugin = {
 	init: () =>  new Promise( resolve => setTimeout( resolve, 3000 ) )
-} );
+};
+Reveal.registerPlugin( 'myPlugin', MyPlugin );
 Reveal.addEventListener( 'ready', () => console.log( 'Three seconds later...' ) );
 Reveal.initialize();
 ```
 
-If the init method does _not_ return a Promise, it is considered ready right away and will not hold up the reveal.js startup sequence.
+If the init method does _not_ return a Promise, the plugin is considered ready right away and will not hold up the reveal.js startup sequence.
 
 ### Retrieving Plugins