consider repository restructuring and build system

[sgratzl]

one could restructure the repo in the following way for better structure and readability

/dist
  cola.umd.js ... umd js build
  cola.esm.js ... esm build
  cola.umd.min.js ... umd minified js build
/src ... moved from WebCola/src
/test ... moved form WebCola/test
/website ... moved form WebCola

build system wise, one could

• move from travis to github actions
• move from phantom-js custom implementation to cypress integration tests
• move from grunt to rollup/webpack for better bundling or use a wrapper like tsdx or microbundle
• move from qunit to jest
• use a service like netlify.com to build and host the website. Alternatively use a github action to build the website and push it back into the gh-pages branch