Add modify demo.
Merge pull request #1 from eskimoblood/master

Add load method and start API block in README
Improve API documentation.
Remove animation slider.
Minimum distance should be 1.
Fix live sliders in Firefox.
Refactor drawing functions, so that all functions now work on a graph.

- a graph has now `draw` ,`drawMetrcis` and `drawPoints` function
- every function works with canvas and SVG
- decouple the rendering from `graph`
- update API doc and example