Tried to reproduce the work of C Bonnet.

Fail because of unknown bug with simulation.py file.
More details in Carole_Bonnet.py located in src\scripts.
Workaround to isolate the cohorte.py bug.

Nose functions correctly. Appears that the data make python to generate a string instead of a number.
Merge pull request #18 from jsantoul/master

Workaround to isolate the cohorte.py bug.