Merge pull request #386 from MarijnS95/zeromq-src-0.3

Upgrade `zeromq-src` to `0.3`

Author: Jasper-Bekkers

zmq-sys/Cargo.toml

@@ -20,7 +20,7 @@ libc = "0.2.15"
 
 [build-dependencies]
 system-deps = "6"
-zeromq-src = { version = "0.2.1" }
+zeromq-src = "0.3"
 
 [package.metadata.system-deps]
 libzmq = "4.1"