Merge pull request #156 from nanan9177/tutorial

Updated instructions for turtle 4.
Reduce use of read pool until we can ensure it doesn't try to write to it.
Close dialog when escape key is pressed. This also discontinues the video.
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Up the default number of production unicorn procs
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Change blockly root to go based off document host instead of asset_host.
Add new ajax loaded hero unit
Change css to better fit user menu into pegasus
Try to add headers to allow x domain.
Change css to better fit user menu into pegasus
Add headers to correct directive (location).
Revert "Change blockly root to go based off document host instead of asset_host."

This reverts commit fe119fd9d56e1ac48a6b6d12b041ace02a46cd29.
Use "sign in" button, instead of sign in/up text.

Also hide "sign in" on all sign in/up, account pages
Try to come up with styles that work on both code.org and learn.code.org css
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Log request time in nginx access logs
Fix arabic config
Add line to GA config to allow cookie sharing with code.org