Docs: webassets core now longer has the gzip filter.
Added EXTRA to assets tag render context, similar to Jinja2
Fix race condition during assets.py collection.

Close #12.
Fix lockup from 08407c4. Close #23.
Fixed a little typo on README.rst

Fixed a little typo on README.rst
Python 3.3 fixes.
Python 3.3 fix for management command.
Unicode-String
Correct Unicode test
Actually depend on an unstable version of webassets