Concept of Zero - Going into multidimensional math
Merge branch 'master' of https://github.com/defm03/hardway-programming

* 'master' of https://github.com/defm03/hardway-programming:
  Update README.md
  function for checking input - if NotANumber do alert
  js function for changing style -> color
  Image change -bulb off/on by onclick
  javascript learning -test of basic function