Replaced dead link to HAC (#163)

The link to the Handbook of Applied Cryptography went stale.

README.md

@@ -100,7 +100,7 @@ A curated list of cryptography resources and links.
 - [An Introduction to Mathematical Cryptography](http://www.math.brown.edu/~jhs/MathCryptoHome.html) - Introduction to modern cryptography.
 - [Crypto101](https://www.crypto101.io/) - Crypto 101 is an introductory course on cryptography.
 - [Cryptography Engineering](https://www.schneier.com/books/cryptography_engineering/) - Learn to build cryptographic protocols that work in the real world.
-- [Handbook of Applied Cryptography](http://cacr.uwaterloo.ca/hac/index.html) - This book is intended as a reference for professional cryptographers.
+- [Handbook of Applied Cryptography](https://cacr.uwaterloo.ca/hac/) - This book is intended as a reference for professional cryptographers.
 - [Introduction to Modern Cryptography](http://www.cs.umd.edu/~jkatz/imc.html) - Introductory-level treatment of cryptography written from a modern, computer science perspective.
 - [OpenSSL Cookbook](https://www.feistyduck.com/library/openssl-cookbook/) - The book about OpenSSL.
 - [Practical Cryptography for Developers](https://cryptobook.nakov.com) - Developer-friendly book on modern cryptography (hashes, MAC codes, symmetric and asymmetric ciphers, key exchange, elliptic curves, digital signatures) with lots of code examples.