Add video.js as YouTube fallback player
Ensure tab parameters survive player swap
some testing and minor refactoring in one of our hairier methods in preparation for future changes
Refactor fallback callback
Remove link to less-good rbenv install guide
remove include of jquery.placeholder because it's already included by asset pipeline
new groupdrag feature
clarify feature description
Merge pull request #471 from code-dot-org/groupdrag

[Finishes #69562218] new groupdrag feature
Add dashboard clone step
Add instructions for browserstack testing of YouTube fallback
Add explicit fallback player width for IE9. Prefer Flash player for IE9.
cr feedback: comment about the duplicate routes, remove random cryptic comment, more route testing
Merge pull request #470 from code-dot-org/activities-milestone-testing

some testing and minor refactoring in ActivitiesController#milestone in preparation for future changes
Use `gem install bundler` first instead of `gem install bundle`
Add notes on testing production locally
Add rmagick Ubuntu dependencies
Update README.md
Merge pull request #469 from code-dot-org/fix-jquery-placeholder-404

Fix jquery placeholder 404
Clean up video.js player on modal close. Give video.js players unique IDs. Add thumbnail info to video links.