For Development.

[BPrathap]

How to setup the dev Environment ?

Example in custom/index.html ( in script tag src="../../src/eventDrops.js") instead of src point to lib. for debugging... but error is throwing.. error : Module name "util/configurable" has not been loaded yet for context: _. Use require([])

[ThieryMichel]

This project use browserify. It cannot work if you try to include individual file on the page.
To develop, you report your change to src/eventDrop.js by calling make browserify.
To ease development you will probably want to remove minification in which case simply call

node_modules/browserify/bin/cmd.js lib/main.js > src/eventDrops.js

[ThieryMichel]

I just added gulp, it should ease development.