revert back to browserify

reasons:
1. running travis build on old nodejs versions. Somehow travis cli was failing to install webpack with old version of node
2. generating bundle file without cli code
3. reference package.json main property to node module instead of generated js file

Author: amitguptagwl

.travis.yml

@@ -1,5 +1,7 @@
 language: node_js
 node_js:
+  - 4
+  - 5
   - 6
   - 7
   - 8