Add tips section

[KevCaz]

In this PR:

• new section "tips"
• trick or tips post have been moved to this section
• Tuto section now includes our "R in Space" series and still need some work
• many changes in layouts:
  • new single layouts (tuto and wiki)
  • new partial "bottom" to include call to Disqus Tocify and Mathjax
  • jquerry and jquerry-ui are now included in /statc/js/
  • use the latest version of Mathjax