Merge pull request #159 from nanan9177/tutorial

Moved Artisted 4_* levels into 20-Hour Curriculum.
redeem prizes working
Update videos
Update default nginx config to only normalize rails traffic (not static assets)
remove dummy_prizes from all
Merge branch 'master' of github.com:code-dot-org/dashboard
Fix "show notes" tab localization
PR feedback + minor fixes
Merge pull request #160 from code-dot-org/redeem_prizes

redeem prizes working
Translations
Fix tests
refactor response generation
RTL!
Tweak path in dev_setup.sh
fix URLs in mail messages, add BETA warning
Merge pull request #161 from code-dot-org/redeem_prizes

redeem prizes cleanup (PR feedback)
[Partial of 59814228]: make dialog wider
Serve video thumbnails from CDN
Translations
Simplify injected html to allow host sites to apply styles