Update analytics snippet for Optimizely + GA
Merge pull request #2879 from gratipay/optimizely-GA

Update analytics snippet for Optimizely + GA
Vendor in dependencies for Balanced API client
Vendor in deps for libsass
Vendor in deps for mandrill and Babel
Vendor in deps for testing

And move mock from requirements.txt to requirements_test.txt.
Remove request.fs from cache_static
Shelve