README: misc updates

README.md

@@ -2,6 +2,14 @@
 
 [![Build Status](https://travis-ci.org/phpseclib/phpseclib.svg?branch=1.0)](https://travis-ci.org/phpseclib/phpseclib)
 
+## Supporting phpseclib
+
+- [Become a backer or sponsor on Patreon](https://www.patreon.com/phpseclib)
+- [One-time donation via PayPal or crypto-currencies](http://sourceforge.net/donate/index.php?group_id=198487)
+- [Subscribe to Tidelift](https://tidelift.com/subscription/pkg/packagist-phpseclib-phpseclib?utm_source=packagist-phpseclib-phpseclib&utm_medium=referral&utm_campaign=readme)
+
+## Introduction
+
 MIT-licensed pure-PHP implementations of an arbitrary-precision integer
 arithmetic library, fully PKCS#1 (v2.1) compliant RSA, DES, 3DES, RC4, Rijndael,
 AES, Blowfish, Twofish, SSH-1, SSH-2, SFTP, and X.509
@@ -28,17 +36,21 @@ AES, Blowfish, Twofish, SSH-1, SSH-2, SFTP, and X.509
 * Modernized version of 1.0
 * Minimum PHP version: 5.3.3
 * PSR-4 autoloading with namespace rooted at `\phpseclib`
-* Install via Composer: `composer require phpseclib/phpseclib ~2.0`
+* Install via Composer: `composer require phpseclib/phpseclib:~2.0`
 
 ### 1.0
 
 * Long term support (LTS) release
 * PHP4 compatible
 * Composer compatible (PSR-0 autoloading)
-* Install using Composer: `composer require phpseclib/phpseclib ~1.0`
+* Install using Composer: `composer require phpseclib/phpseclib:~1.0`
 * Install using PEAR: See [phpseclib PEAR Channel Documentation](http://phpseclib.sourceforge.net/pear.htm)
 * [Download 1.0.16 as ZIP](http://sourceforge.net/projects/phpseclib/files/phpseclib1.0.16.zip/download)
 
+## Security contact information
+
+To report a security vulnerability, please use the [Tidelift security contact](https://tidelift.com/security). Tidelift will coordinate the fix and disclosure.
+
 ## Support
 
 Need Support?