Updated to native_tls, rustc 2021 edition, and created an example directory.

[641i130]

I simply replaced a few bits of code swapping out the openssl bits to the native_tls alternative, addressing #16. I also moved the example to the example directory enabling the use of (addressing #13 ): cargo run --example gmail

Please confirm I did this right! I'll fix any issues with this as soon as possible.