Update README.md

Added digestpp

README.md

@@ -232,6 +232,7 @@ A curated list of awesome C/C++ frameworks, libraries, resources, and shiny thin
 * [BeeCrypt](http://beecrypt.sourceforge.net/) - A portable and fast cryptography library. [LGPLv2.1+]
 * [Botan](http://botan.randombit.net/) - A crypto library for C++. [BSD-2]
 * [Crypto++](https://github.com/weidai11/cryptopp) - A free C++ class library of cryptographic schemes. [Boost] [website](http://www.cryptopp.com/)
+* [digestpp](https://github.com/kerukuro/digestpp) - C++11 header-only message digest (hash) library. [PublicDomain]
 * [GnuPG](https://www.gnupg.org/) - A complete and free implementation of the OpenPGP standard. [GPL]
 * [GnuTLS](http://www.gnutls.org/) - A secure communications library implementing the SSL, TLS and DTLS protocols. [LGPL2.1]
 * [Libgcrypt](http://www.gnu.org/software/libgcrypt/) - A general purpose cryptographic library originally based on code from GnuPG. [LGPLv2.1+]