function capitalize(str) {
        return (str.charAt(0).toUpperCase() + str.slice(1));
}
Verify HMAC against shared secret.  You are expected to pass in an object
that was returned from `parse()`.

@param {Object} parsedSignature the object you got from `parse`.
@param {String} secret HMAC shared secret.
@return {Boolean} true if valid, false otherwise.
@throws {TypeError} if you pass in bad arguments.
@throws {InvalidAlgorithmError}