Security
- Use hmac.compare_digest instead of plain == by [Compro-Prasad](https://github.com/Compro-Prasad) in [#3](https://github.com/nogoodusername/simple-otp/pull/3)
- Make use of cyptographically secure random numbers by [Compro-Prasad](https://github.com/Compro-Prasad) in [#4](https://github.com/nogoodusername/simple-otp/pull/4)