Log Message:
Version 0.40

WeasyPrint now depends on cssselect2 instead of cssselect and lxml.

New features:
* Named pages.
* Unprefix properties
* Add a "verbose" option logging the document generation steps.

Bug fixes:
* Fix slow performance with long pre-formatted texts.
* Improve speed and memory usage for long documents.
* Don't crash on local() fonts with a space and no quotes.