Update readme with composer usage

README.md

@@ -14,22 +14,43 @@ Image Processing Queue also accommodates responsive themes much better than OTF.
 
 To install Image Processing Queue as a plugin search for "[Image Processing Queue](https://wordpress.org/plugins/image-processing-queue/)" in your WordPress dashboard and install it from there.
 
-### Install as a Theme Library
+### Install as a Library
 
-If you're a theme developer and would like to include Image Processing Queue as a library in your theme, you'll need to clone this repository into your theme:
+If you're a plugin or theme developer you will need to require Image Processing Queue using Composer:
 
 ```
-$ cd /path/to/wordpress/wp-content/themes/your-theme/
-$ git clone git@github.com:deliciousbrains/wp-image-processing-queue.git image-processing-queue
-$ composer install
+$ composer require deliciousbrains/wp-image-processing-queue
 ```
 
-You'll also need to add the following to your functions.php file:
+The following boilerplate will need adding to your project, which will load the required files and ensure WP cron processes the images in the background:
 
 ```php
-require_once get_stylesheet_directory() . '/image-processing-queue/image-processing-queue.php';
+require_once '/vendor/autoload.php';
+wp_queue()->cron();
 ```
 
+The following database tables will also need creating:
+
+```sql
+CREATE TABLE {$wpdb->prefix}queue_jobs (
+id bigint(20) NOT NULL AUTO_INCREMENT,
+job longtext NOT NULL,
+attempts tinyint(3) NOT NULL DEFAULT 0,
+reserved_at datetime DEFAULT NULL,
+available_at datetime NOT NULL,
+created_at datetime NOT NULL,
+PRIMARY KEY  (id)
+
+CREATE TABLE {$wpdb->prefix}queue_failures (
+id bigint(20) NOT NULL AUTO_INCREMENT,
+job longtext NOT NULL,
+error text DEFAULT NULL,
+failed_at datetime NOT NULL,
+PRIMARY KEY  (id)
+```
+
+You can use the `wp_queue_install_tables()` helper function to create the required database tables. This should be called from within an [activation hook](https://developer.wordpress.org/reference/functions/register_activation_hook/) or custom upgrade routine.
+
 ## Usage
 
 When you want to output an image in your theme, simply call the `ipq_get_theme_image()` function passing in the ID of the image post, an array of sizes you've decided on for the image in this particular context, and an array of additional HTML attributes for the `<img>` tag: