To start virtual machine:
$ vagrant up
(will download Centos 7, install Docker, grab eXist-DB Docker image, and run eXist as daemon; port 8080 forwarded to localhost on host machine)
To install node packages:
$ npm install
To copy files to eXist-DB:
$ gulp4 build && gulp4 copy
To watch for changes and build/copy automatically:
$ gulp4 watch
Edit gulpfile.js
to configure.