Add support for private npm repo for testing

### Do you want to request a feature, report a bug, or improve documentation?
request a feature

### If you are reporting a bug?

**What is the current behavior?**

**What is the expected behavior?**

**What are the steps to reproduce?**

**What OS are you using and what version of node.js and @bluehalo/node-fhir-server-core are you running?**
