Small clean at Markdown from IPYNB

ae6ccd8 change the template to avoid unnecessary HTML syntax at Markdown files. **Code samples still use HTML syntax because `print` has an unwanted `\n`.**

69b026d update the Markdown files based on ae6ccd8. This one is machine generated.

This PR should close #644.

@cboettig and @jdblischak 

> He does this for consistency with the python markdown format, but I'm afraid I don't understand what markdown flavour is being rendered for the python examples or how it is being generated.

Thanks to point this bug and I hope this PR solve it. The reason that the markdown files create from ipynb are almost a HTML file is that I forgot of some features from kramdown.