v2.0.0

What changed

• issuer and account_name are now members of TOTP, and thus are not used anymore as function parameters for methods
• from_url() now extracts issuer and label
• Method get_url() now needs otpauth feature
• Method get_url() now produces more correct urls
• Methods next_step(time: u64) and next_step_current will return the timestamp of the next step's start
• Feature qr enables feature otpauth

Special thanks

• @wyhaya for giving ideas and feedback for this release