Override SHA1 encryption in `sorcery` gem

* Override SHA1 encryption used by Sorcery to
make Sorcery compatible with Devise
* This has been moved here out of our fork of
sorcery (https://github.com/amaabca/sorcery/commit/e5efc6f267d915bdd6b9b10512a211cdc86b9f4d).
The code itself is blatantly stolen from @RyanoonRails
Merge pull request #1 from amaabca/override-sha1-encryption

Override SHA1 encryption in http://rubygems.org/gems/sorcery