Update rustls version to 0.5.8 to make it work with nightly compiler.

[timgluz]

Hi,

thanks for your library! I'm using it to get around of OpenSSL nightmares on different platforms.

I encountered a compiler error when i tried to compile my project with nightly rustc.
Error is caused by old version of rustls, which is using unknown compiler feature #[export_macro]. That issue is now fixed in 0.5.8 . source: rustls/rustls#55

Is it welcome to submit PR that upgrades just that dependency?
ps: I'm not in hurry and i can wait for next release.

[bruceadams]

@timgluz The dependency here on rustls is rustls = "0.5.6" which allows for higher minor versions, including 0.5.8. Can you try doing cargo update in your project that uses hyper-rustls?

For what it's worth, my project https://github.com/bruceadams/wdsapi depends on hyper-rustls and my concrete use (where I have Cargo.lock checked into source control) is in https://github.com/bruceadams/wdscli, see https://github.com/bruceadams/wdscli/blob/master/Cargo.lock#L105:L112 which shows rustls 0.5.8 as a dependency of hyper-rustls.

[timgluz]

Hi,

thanks. It worked.