Remove references to an injectable CSPRNG in the docs

Author: SammyK

docs/reference.md

@@ -91,4 +91,3 @@ You can overwrite certain functionality of the SDK by coding to an interface and
 | `Facebook\Http\GraphRawResponse`  | An entity that is returned from an instance of a `FacebookHttpClientInterface` that represents a raw HTTP response from the Graph API.  |
 | [`Facebook\PersistentData\PersistentDataInterface`](reference/PersistentDataInterface.md) | An interface to code your own persistent data storage implementation.  |
 | [`Facebook\Url\UrlDetectionInterface`](reference/UrlDetectionInterface.md) | An interface to code your own URL detection logic.  |
-| [`Facebook\PseudoRandomString\ PseudoRandomStringGeneratorInterface`](reference/PseudoRandomStringGeneratorInterface.md) | An interface to code your own cryptographically secure pseudo-random string generator.  |

docs/reference/Facebook.md

@@ -52,7 +52,6 @@ $fb = new Facebook\Facebook([
   'http_client_handler' => 'guzzle',
   'persistent_data_handler' => 'memory',
   'url_detection_handler' => new MyUrlDetectionHandler(),
-  'pseudo_random_string_generator' => new MyPseudoRandomStringGenerator(),
 ]);
 ```
 
@@ -116,29 +115,6 @@ $fb = new Facebook([
 
 If any other value is provided an `InvalidArgumentException` will be thrown.
 
-### `pseudo_random_string_generator`
-Allows you to overwrite the default cryptographically secure pseudo-random string generator.
-
-Generating random strings in PHP is easy but generating _cryptographically secure_ random strings is another matter. By default the SDK will attempt to detect a suitable to cryptographically secure random string generator for you. If a cryptographically secure method cannot be detected, a `Facebook\Exceptions\FacebookSDKException` will be thrown.
-
-You can force a specific implementation of the CSPRSG's provided in the SDK by setting `pseudo_random_string_generator` to one of the following methods: `mcrypt`, `openssl` and `urandom`.
-
-```php
-$fb = new Facebook([
-  'pseudo_random_string_generator' => 'openssl',
-]);
-```
-
-You can write your own CSPRSG that implements the [`Facebook\PseudoRandomString\PseudoRandomStringGeneratorInterface`](PseudoRandomStringGeneratorInterface.md) and set the value of `pseudo_random_string_generator` to an instance of your custom generator.
-
-```php
-$fb = new Facebook([
-  'pseudo_random_string_generator' => new MyPseudoRandomStringGenerator(),
-]);
-```
-
-If any other value is provided an `InvalidArgumentException` will be thrown.
-
 ## Environment variables fallback
 
 The only required configuration options are `app_id` and `app_secret`. However, the SDK will look to environment variables for the app ID and app secret.

docs/reference/FacebookRedirectLoginHelper.md

@@ -126,7 +126,7 @@ Most modern web frameworks have custom session handlers that allow you to manage
 
 ### CSPRNG
 
-The CSRF value that the `getLoginUrl()`, `getReRequestUrl()`, and `getReAuthenticationUrl()` methods generate are all _cryptographically secure_ random strings. PHP's native support of CSPRNG's is spotty at best. The PHP SDK goes to great lengths to to detect a suitable CSPRNG but in rare cases, it might not find a suitable one. The [`PseudoRandomStringGeneratorInterface`](PseudoRandomStringGeneratorInterface.md) allows you to inject your own custom CSPRNG.
+The CSRF value that the `getLoginUrl()`, `getReRequestUrl()`, and `getReAuthenticationUrl()` methods generate are all _cryptographically secure_ random strings. To generate these tokens the PHP SDK uses the [CSPRNG functions in PHP 7](http://php.net/csprng) and the [paragonie/random_compat](https://github.com/paragonie/random_compat) polyfill for PHP 5.6.
 
 
 ### URL detection