Fix #1232: Add webpack:watch gulp task

Procfile

@@ -1 +1,2 @@
 web: npm start
+webpack: npm run webpack:watch

gulpfile.js

@@ -192,6 +192,10 @@ gulp.task('webpack', ['build'], function() {
     .pipe(gulp.dest('demo/dist/'));
 });
 
+gulp.task('webpack:watch', ['webpack'], () => {
+  gulp.watch('./src/*', ['webpack']);
+});
+
 /**
  * Submit coverage results to coveralls.io
  */

package.json

@@ -75,7 +75,6 @@
     "zmodem.js": "^0.1.5"
   },
   "scripts": {
-    "prestart": "gulp webpack",
     "start": "node demo/app",
     "prestart-zmodem": "npm run build",
     "start-zmodem": "node build/addons/zmodem/demo/app",
@@ -86,7 +85,8 @@
     "build": "gulp build",
     "prepublish": "npm run build",
     "coveralls": "gulp coveralls",
-    "webpack": "gulp webpack"
+    "webpack": "gulp webpack",
+    "webpack:watch": "gulp webpack:watch"
   },
   "dependencies": {}
 }