Update django-recaptcha to latest version to remove artificial dependency on django-registration.

See https://github.com/praekelt/django-recaptcha/commit/18812b92b041bcd289be658feb29d9ac8aa52f96
Use wheelball for vagrant setup and switch to Python2.6.
Install Django from PyPI because 1.4.x can't be installed flawlessly via a wheel file.
Fix jingo error.
Added apt cache.
Fixed SyntaxError in test.
Use secure URL for Vagrant box.
Added invoke task to build wheelball of the compiled requirements for travis.
Trying using aria2 instead.
Because I can't read manpages.
Create a non-root virtualenv.
Create the cache dir correctly.
Make sure the order of directory creation is correct.