Added ENV for dead-code elimination in production mode

env/development.js

@@ -0,0 +1,5 @@
+module.exports = {
+    production: false,
+    development: true,
+    node: false
+};

env/node.js

@@ -0,0 +1,5 @@
+module.exports = {
+    production: true,
+    development: false,
+    node: true
+};

env/production.js

@@ -0,0 +1,5 @@
+module.exports = {
+    production: true,
+    development: false,
+    node: false
+};