Updated dependencies' versions: nose, lxml

I'd rather use lxml>=2.3.3. It allows to run an old version for those who want to - it's definitely works with 2.3.3 i.e. it's not like you have to use 3.3.1. At the same time it'll allow using newer version - 3.3.1 where they probably fixed some bugs, etc. Have you tried running tests with lxml==3.3.1? It's a major lib upgrade from 2 to 3 so some interface functions might have changed, etc.