Add java.awt.headless to default java opts

Author: hugoduncan

project.clj

@@ -14,4 +14,5 @@
                  [com.jcraft/jsch.agentproxy.pageant ~agentproxy-version]
                  [com.jcraft/jsch.agentproxy.core ~agentproxy-version]
                  [com.jcraft/jsch.agentproxy.jsch ~agentproxy-version]
-                 [com.jcraft/jsch "0.1.51"]])
+                 [com.jcraft/jsch "0.1.51"]]
+  :jvm-opts ["-Djava.awt.headless=true"])