UI changes to learn.code.org root and sign-in pages.  Also header's link to sign up goes to root.
The teacher now has an option to print certificates for students who have finished 20hours.
Fixes to UI update based on feedback.
Merge pull request #280 from nanan9177/feedback_collect

Feedback collect
Add instructions to level so that teachers can make custom instructions.
Don't truncate scripts or script levels because we are going to start allowing teachers to create scripts and script levels.
Small fixes to 20 hour certificate generation.
Merge branch 'master' of https://github.com/code-dot-org/dashboard
Merge pull request #279 from code-dot-org/ui

UI changes to learn.code.org
Teachers get link to blog in dashboard home.
Merge pull request #282 from code-dot-org/bloglink

Teachers get link to blog in dashboard home.
Record Google Analytics custom variable for signed-in.
PR feedback. Fix seed task to use where/first_or_create. Prioritize yml instructions over db. Only allow admins to create levels.
Merge pull request #281 from code-dot-org/builder

Add instructions to level so that teachers can make custom instructions.
Merge pull request #283 from code-dot-org/analytics

Record Google Analytics custom variable for signed-in.
Translations
Fix sync script
Fix quote marks in analytics for signed-in user.
Merge branch 'master' of https://github.com/code-dot-org/dashboard
Any user can be added as hint editor by admin.