[WIP] Update dependencies.

[stephank]

Notable upgrades are Hyper 0.10, Iron 0.5 and the openssl crate 0.9, among
smaller dep upgrades. Only the openssl crate upgrade required code changes.

Waiting on:

• staticfile: [WIP] iron-0.5 update iron/staticfile#91
• lettre: feat(transport): Upgrade to OpenSSL ^0.9 lettre/lettre#112
• ring: Allow exporting public components of RSAKeyPair. briansmith/ring#441

[stephank]

I've created a second branch where I've completely replaced OpenSSL with hyper-native-tls and ring. It'll only be used as a dependency of hyper-native-tls on Linux.

https://github.com/portier/portier-broker/compare/featureDeps2

It's almost finished, but requires some changes in ring too:

• Extract RSAKeyPair public components so we can build a JWK
• Use a JWK to verify a signature

[stephank]

Alright, I've now pushed the ring-based branch to this PR! It depends on my in-progress branch of ring, but is working nicely. :)

Once mature, we may even be able to switch to rustls. :)

[coveralls]

Changes Unknown when pulling 81ae8ae on featureDeps into ** on master**.

[coveralls]

Changes Unknown when pulling 5f71583 on featureDeps into ** on master**.

[stephank]

I'm closing this, because I'm currently not motivated to push along the upstream changes, which have bitrotten, just as this branch.

I'll clean up the branches in a bit. :)