force pyparsing < 2

pyparsing 2.0 doesn't work with python 2 anymore.
store a flag in nuwiki if articles are already expanded

don't expand them if they were already expanded.
fetch expanded articles
require python 2.6, up version to 0.15.0

also don't test on python 2.5
merge the 'fetch-expanded-article' branch
install via entry points

I know I did the exact opposite, but that was when I had to build
debian packages.