Close open handlers on exit

cli.js

@@ -39,4 +39,13 @@ command.run(process.argv.slice(2), options, function(err) {
 
   // Don't exit if no error; if something is keeping the process open,
   // like `truffle console`, then let it.
+
+  // Clear any polling or open sockets - `provider-engine` in HDWallet
+  // and `web3 1.0 confirmations` both leave interval timers etc wide open.
+  const handles = process._getActiveHandles();
+  handles.forEach(handle => {
+    if (typeof handle.close === 'function'){
+      handle.close();
+    }
+  })
 });