correction

retour a une fonction get_value plus complexe
Merge pull request #141 from AlexisEidelman/datatable

correction
getting closer

seems to have problem only when we mix fam and foy or men and foy, etc
Merge pull request #145 from AlexisEidelman/datatable

getting closer
Merge branch 'datatable' of https://github.com/openfisca/openfisca into datatable