Upgrade Jetty

[black-snow]

We're still using Jetty 9.4.10 while the current version is already 9.4.18.
There's at least one breaking change in 9.4.17:

• 3464 Split SslContextFactory into Client and Server

which blows up my current project for another dependency in my fat jar includes a 9.4.18 jetty leading to a NoClassDefFoundError.

Can we upgrade to the latest jetty version? I'll try to file a PR if I find some spare time.

[black-snow]

My crash is gone with dropwizard 1.3.10. I'ma file a PR with some dep updates.

[black-snow]

PR here: #27