Fix gulp test task

jest.runCLI() was being called with only 1 argument, there was a mis-bracketing
which lead to this. When trying to fix the bracketing here, I realised the
error handling callback also did not work correctly (done was undefined), and
the 'test' task considered itself succeeded before the tests were even run.

I've refactored the task a little to successfully "fail" when the tests fail,
which means that "gulp test" will now return a non-zero exit code when the
tests fail.

gulpfile.js

@@ -15,8 +15,8 @@ gulp.task('webserver', function() {
   connectTask();
 });
 
-gulp.task('test', function() {
-  jestTask();
+gulp.task('test', function(callback) {
+  return jestTask(callback);
 });
 
 gulp.task('scripts', function() {

tasks/jest.js

@@ -1,5 +1,4 @@
 var jest = require('jest-cli');
-var gutil = require('gulp-util');
 var configs = require('./configs');
 
 var jestConfig = {
@@ -10,8 +9,12 @@ var jestConfig = {
   verbose: false
 };
 
-module.exports = function() {
-    jest.runCLI({ config: jestConfig }), configs.paths.source, function() {
-      done().on('error', gutil.log);
-    };
+module.exports = function(callback) {
+    jest.runCLI({ config: jestConfig }, configs.paths.source, function(result) {
+      if (!result || !result.success) {
+        callback('Jest tests failed')
+      } else {
+        callback()
+      }
+    });
 };