Added length type check to HOTP and corresponding test
Add MGF1 MD selection function (available in OpenSSL 1.0.1+)
Updated documentation for HOTP and TOTP TypeError
Merge pull request #721 from reaperhulk/pss-funcs

Add MGF1 MD selection function (available in OpenSSL 1.0.1+)
Merge pull request #720 from Ayrx/hotp-length-type-check

Added length type check to HOTP and corresponding test
Merge remote-tracking branch 'upstream/master'