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.
Update deps for aspen-jinja
Add another testing dependency
Update pip/setuptools/virtualenv

Picks up some bug-fix related to case sensitivity in package names.
Upgrade rsa lib to avoid a distribute download

Older Python packages used a hack to install a more or less random
version of distribute during their own installation.
Merge pull request #2880 from gratipay/add-some-deps

vendor in missing deps