Merge pull request #1 from scarpentier/master

added a link to Subgraph website
Merge pull request #2 from scarpentier/master

Fixed urls
april teaser
april edition first annoucement
small fixes (bullets, spacing, proper header)
added network track challenge description
tonight's challenges
wrapped-up April edition into archives

Added a few fancy ToC style links
added a link to presenting...
added march's pictures, challenge files and write-up
event template for lazy people like me
forgot to commit april write-up, here it is
minor improvements and small fixes to template
added stay-tuned template
June edition
eventbrite stuff in template
eventbrite stuff for June edition
added link to shared google calendar
june edition over moved to archive and links to write-up
prettier link separation