README.md instead of rst

[amureki]

1. Switch rst to md
2. Add a basic example to catch attention
3. Add some more things to MANIFEST.in
4. setup.py improvements

[amureki]

@model-bakers/core what do you think about switching README to md format?
It is much easier to work with (at least in my opinion) and pypi supports it as well.

I've added some unrelated updates to setup.py since I was on it... But we can do it separately.

[berinhard]

Thanks for helping with this! Maybe we can also migrate our docs at some point to format it using Markdown with Sphinx. I created #47 to address that.

[anapaulagomes]

Wasn't this PR a WIP? @berinhard @amureki

[amureki]

@anapaulagomes @berinhard I was just not sure if you would have some suggestions on top of it. But we anyways can iterate further if needed, that's a good changing point. :)

[anapaulagomes]

Alright then! 👍 Thanks @amureki and @berinhard!