Move styles into css file and create more example elements
Create own exception class
Move non-importable source files into src directory
Several changes

* Create animation manager class.

* Fix using easing algorithms wrongly.

* Use exceptions when applicable.

* Do not allow multiple animation for the same element and property
  simultaneously.

* Allow multiple properties to be specified.
Use types and de-minimize code
Use new animate interface

Add more elements animating simultaneously.