Use send() not process.send().

Some process.send()s were added on master, but they should be just
send() so they use the serialization stuff.

lib/juttle-subprocess.js

@@ -9,7 +9,7 @@
 var JuttleLogger = require('juttle/lib/logger');
 JuttleLogger.getLogger = function(name) {
     function log(level, args) {
-        process.send({
+        send({
             type: 'log',
             name: name,
             level: level,
@@ -105,15 +105,15 @@ process.on('message', function(msg) {
             // errors/warnings/sink data.
             program.events.on('error', function(msg, err) {
                 logger.error(msg, err);
-                process.send({
+                send({
                     type: 'error',
                     error: err
                 });
             });
 
             program.events.on('warning', function(msg, warn) {
                 logger.warn(msg, warn);
-                process.send({
+                send({
                     type: 'warning',
                     warning: warn
                 });