Update 2012-07-11-globals-hour.md

Grammar updates.
Update 2012-07-13-globals-screen.md

Grammar edits.
Merge pull request #9 from gueroJeff/patch-2

Update 2012-07-13-globals-screen.md
Merge pull request #8 from gueroJeff/patch-1

Update 2012-07-11-globals-hour.md
Modify image sizes
Remaining learn chapters, inspired by Stas's blog posts
And the updated menu
Merge branch 'master' of github.com:l20n/l20n.org