add standard datasets from openml

[dvro]

In http://www.openml.org/, there are thousands of datasets for several domains. This issue refers to selecting popular datasets that fit into different categories on awesome-datasets.

[mridulg]

@dvro How many datasets per section do you need?

[dvro]

@mridulg this is a curated list, the more the better. But keep in mind to select only "awesome" datasets, where awesome is either due dataset quality or popularity (on papers, tutorials ...). "Awesome" is subjective; feel free to add any data you think is awesome.

[mridulg]

Ok. On it.