Added independent chart examples.

This PR fixes #1014.
Yes, I generally agree... my intention here (with all the 4 examples) is to show the people you can do several pre-manipulations and drop the data into the chart interface... the iris_scatter example just do exactly what you described... data>>pd>>chart in a few lines... I just wanted to give a wide vision of possibilities, with something of pre-manipulation, but if you think is better to show all examples with just a few lines, which can be a valid option too, I can consider that too...