Bump to Oscar 0.6.3 in tox.ini
Include STATIC_ROOT for tests

It's needed by django-compressor==1.3
Remove purl from install_requires

Oscar>=0.6 already includes it.
Use correct tagline for sandbox

Plus remove static dirs.
Prettify the sandbox payment details template
Use timezones in sandbox
Upgrade dependencies in requirements.txt
Re-apply offers when loading frozen basket