Point Node.js API reference to landing page

Seems that Node.js 4.0 API reference now has a list of exports, which should be less confusing for users.

Previously we were pointing to the modules page to make this easier for users: https://docs.couchbase.com/sdk-api/couchbase-node-client/modules.html 

Let's change the API Reference to the landing page now that this is fixed: https://docs.couchbase.com/sdk-api/couchbase-node-client/index.html