README: add note on how to install

Author: terrafrost

README.md

@@ -4,6 +4,14 @@
 
 PHP 5.x polyfill for mcrypt extension.
 
+## Installation
+
+With [Composer](https://getcomposer.org/):
+
+```
+composer require phpseclib/mcrypt_compat
+```
+
 ## Supported algorithms
 
 - rijndael-128
@@ -37,4 +45,4 @@ PHP 5.x polyfill for mcrypt extension.
 - nofb
 - stream
 
-Although `ncfb` and `nofb` are supported `cfb` and `ofb` are not. Further, mcrypt_compat's `ncfb` implementation has some incompatibles with mcrypt's implementation where `mcrypt_generic` and `mdecrypt_generic` are concerned. The unit tests elaborate.
+Although `ncfb` and `nofb` are supported `cfb` and `ofb` are not. Further, mcrypt_compat's `ncfb` implementation has some incompatibles with mcrypt's implementation where `mcrypt_generic` and `mdecrypt_generic` are concerned. The unit tests elaborate.