Update travis.preinstall.sh to apt update and install libzmq3-dev

Author: metadings

travis.preinstall.sh

@@ -23,6 +23,7 @@ if [ "$(uname)" = "Darwin" ] ; then
 
   else # if [ "INSTALL_LIBZMQ_MACOS" == "brew" ] ; then
 
+    brew update
     brew install zeromq # --universal
   fi
 
@@ -31,8 +32,8 @@ else # if [ "$(uname)" = "Linux" ]
 #  curl http://download.opensuse.org/repositories/network:/messaging:/zeromq:/release-stable/Debian_9.0/Release.key >Release.key
 #  sudo apt-key add Release.key
 #  sudo add-apt-repository "deb http://download.opensuse.org/repositories/network:/messaging:/zeromq:/release-stable/Debian_9.0 ./"
-#  sudo apt-get update
-  sudo apt-get install libzmq5
+  sudo apt-get update
+  sudo apt-get install libzmq3-dev
 fi
 
 nuget restore clrzmq4.mono.sln