[Rivet] cython version issue

[David Grellscheid]

Hi all,

Peter R. just pointed out that there is no Cython version at the moment 
that will work in Rivet and YODA fresh from hg. Rivet asks for >= 24 (?) 
but that version fails in YODA with the property alias bug we discussed 
before.

How did this get sorted out in Rivet, and can we please do the same in YODA?

Thanks,

   David