Upgrade openssl dependency

[chaoticsmol]

Currently, cookie-rs's Cargo.toml specifies using Rust-OpenSSL version 0.7.0. At the time of this writing, the latest release is version 0.8.2, which includes a number of bug fixes that, in some applications has resolved some functional failings.

I'd like to ask for cookie-rs to adopt these changes and upgrade to the latest version.

[alexcrichton]

Sure!