Add sample of receiving CAS via N1QL and using in SDK with node.js

Because of how javascript processes large numbers, the CAS should usually be handled as a string, not a number.  This can be a bit confusing if the N1QL response is parsed into a JavaScript object.

We should add a section to the documentation that shows an example of this.

Please drop a code snippet in here Brett Lawson and then assign to Tony Hillman to get it integrated into the docs.