Sign and validate JSON objects!
signobj protects your data with SHA-1 HMAC & a 16 bit salt.
secret, you can also pass in some extra
hidden data that
is used when hashing. This can be useful if you're creating an access token,
and you want it to become invalid when they change their password, and also don't
want the password with the public data.
This function returns a Q promise, that resolves the signed & salted data.
Checks to make sure your data is valid. The promise, if resolves successfully, will return your original data.