Improve package deployment. Improve ESLint support. Update deps.

[DoctorBud]

• Clarified the difference between the library build and the demo build
• Added utility scripts to better support debugging of 'npm publish'
• Moved demo/src/ into src/demo
• Updated various dependencies
• update CONTRIBUTING.md to talk about 'pack' and 'buildandserve' scripts.

[nathandunn]

@DoctorBud Tested and looks great. Seems to build okay. I'm going to go ahead and merge and publish this.