Add some documentation

Author: dmitrivereshchagin

README.md

@@ -1,2 +1,103 @@
 # yii-snappy
-Basic wrapper around [Snappy](https://github.com/KnpLabs/snappy) implemented as Yii component
+
+This is a basic wrapper around [Snappy] [s] implemented as [Yii] [y]
+application component.  Snappy is a PHP library that uses
+[wkhtmltopdf and wkhtmltoimage] [w] to render HTML into PDF and various
+image formats.
+
+## Installation
+
+Installation using [Composer] [c] should be straightforward
+
+```
+composer require dmitrivereshchagin/yii-snappy
+```
+
+To register components in your application add something like the
+following in configuration `components` section:
+
+```php
+'pdf' => array(
+    'class' => '\Snappy\PdfComponent',
+    'binary' => '/usr/local/bin/wkhtmltopdf',
+    'options' => array('orientation' => 'landscape'),
+),
+'image' => array(
+    'class' => '\Snappy\ImageComponent',
+    'binary' => '/usr/local/bin/wkhtmltoimage',
+),
+```
+
+Specifying paths to binaries is mandatory.  Optionally you can configure
+default command line arguments that can be overridden or adjusted later.
+
+## Usage
+
+Use `Yii::app()->pdf` and `Yii::app()->image` to generate PDF documents
+and images respectively.  These components provide access to methods
+declared by `\Knp\Snappy\GeneratorInterface`.
+
+Here are some examples.
+
+### Generate image from an URL
+
+```php
+Yii::app()->image->generate('http://example.com', '/path/to/image.jpg');
+```
+
+### Generate PDF document from an URL
+
+```php
+Yii::app()->pdf->generate('http://example.com', '/path/to/document.pdf');
+```
+
+### Generate PDF document from multiple URLs
+
+```php
+Yii::app()->pdf->generate(
+    array('http://example.com', 'http://example.org'),
+    '/path/to/document.pdf'
+);
+```
+
+### Generate PDF document from a view
+
+```php
+Yii::app()->pdf->generateFromHtml(
+    $this->render('view', array('name' => $value), $return = true),
+    '/path/to/document.pdf'
+);
+```
+
+### Generate PDF document as response from controller
+
+```php
+$html = $this->render('view', array('name' => $value), $return = true);
+
+Yii::app()->request->sendFile(
+    'document.pdf',
+    Yii::app()->pdf->getOutputFromHtml($html)
+);
+```
+
+### Generate PDF document with relative URLs inside
+
+```php
+$url = Yii::app()->createAbsoluteUrl('controller/action');
+
+Yii::app()->request->sendFile(
+    'document.pdf',
+    Yii::app()->pdf->getOutput($url)
+);
+```
+
+## Credits
+
+This code is based on Snappy library.  Snappy has been originally
+developed by [KnpLabs] [k] team.
+
+[c]: https://getcomposer.org
+[k]: http://knplabs.com
+[s]: https://github.com/KnpLabs/snappy
+[w]: http://wkhtmltopdf.org
+[y]: https://github.com/yiisoft/yii