Add ParseOtpString function to directly from the Yubikey.
Account for variable-sized OTP strings.
Revert import to original in example.

This was changed to make the example code run with my changes on a local branch; it needs to be reverted for the pull request. Found by dgryski.
Remove untyped returns and Otp->OTP
Merge branch 'ParseOtpString' of github.com:kisom/yubikey into ParseOtpString
Otp->OTP in parse example.
Pub -> PubID
NewOtp -> NewOTP in test
add NewPubID and ParseOTPString tests