Upgrade Node Js library reference to 14.x

We will need to add support for node js library 14.x thats releasing on April 21 2020

Apparently its predecessor 13.x will reach EOL in June 2020. 

Any Couchbase Node.js client that refer to 13.x must start using 14.x after its release in April

 Upgrade o 14.x also came as as request from Cisco. 

Below are some notes from email conversation : 

• Node.js development releases are not officially supported, but are tested against.
• 14.x should become supported in the first release following the April 21, 2020 Node.js release date.
• Node.js release information we follow is available here: https://github.com/nodejs/Release