Update "Contributing to the core"
Merge pull request #1 from aenario/patch-1

Update "Contributing to the core"
Added: permissions section to the data system tutorial
Fixed: minor addition to the DS API cookbook
Updated: vagrant/virtualbox version number
Changed: first letter is now uppercased
Added: spaces
Fixed: typo
Fixed: git clone command to clone a specific branch
Improved: wording
Minor wording improvements
Merge pull request #2 from jsilvestre/master

Minor improvements
typos
add snowden release sticker
update gaols
few typo fixed - index.html.md
typo fixed (wether => whether)- index.html.md
Update index.html.md
few typos fixed in setup-environment.html.md
few typos fixed in first-app.html.md