Update undescore.js to version 1.6 and underscore.string.js to version 2.3
[IMP] Upgrade underscore.js from version 1.3.1 to 1.6.0 and underscore.string.js from version 1.2.0 to 2.3.0
[IMP] Upgrade underscore.js from version 1.3.1 to 1.6.0 and underscore.string.js from version 1.2.0 to 2.3.0