Feature: Markdown README instead of RST

[guillaume-chevalier]

TODO: check if it's possible to use markdown (how).

Neuraxle$ twine check dist/*
Checking dist/neuraxle-0.3.0.linux-x86_64.tar.gz: PASSED, with warnings
  warning: `long_description_content_type` missing.  defaulting to `text/x-rst`.

[vincent-antaki]

@guillaume-chevalier I'd close this issue if its ok with you, rst is fine for our need.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs in the next 180 days. Thank you for your contributions.