pre-GSoC - various updates before adding new studen list

[dpshelio]

This includes a few changes:

• It gets the whole post (Grab whole post, not only summary #34) when available (some blogs only shares a summary through their feed)
• It removes the READ MORE link and uses the native one from Nikola, including the teaser to only the first couple of lines.
• Improves the student list on the page (Improve the student list on the site #33) showing a top full-width bar instead of only on the side, it's mobile-friendly as it renders properly on small screens and includes checkboxes to see student progress (which hides on mobile view).
• It also adds some more explanation on the README (now also on md format!) ([docs] How does it work? #32)
• It includes new sub-orgs logos.