Auto merge of #1666 - sgrif:sg-configurable-server-threads, r=jtgeibel
Auto merge of #1666 - sgrif:sg-configurable-server-threads, r=jtgeibel

Make the number of threads on the server configurable

50 is probably way too high. @jtgeibel and I are interested in seeing
how this is affecting our memory usage, it'd be great to configure this
without a redeploy.

rust-lang/crates.io,rust-lang/crates.io,rust-lang/crates.io,rust-lang/crates.io