2019 update and fix issues

[kcmr]

Issues

• Fix import not working when using Webpack #15

Code

• Use LitElement instead of Polymer
• Use open-wc/testing instead of WCT

Development

• Improve serve (use Parcel bundler)
• Move style to a stylesheet file
• Add eslint config

Release / CI

• Improve CI release config
• Include a bundled release