Adapt API to Openfisca 2.0

[fpagnoux]

• Apply core API changes introduced by openfisca-core 2.0

[cbenz]

Good work, I was doing the same thing in OpenFisca-Parsers too

[fpagnoux]

@cbenz I did a few corrections in parsers, but I'm running into this error. Do you understand where it could come from ?

UPDATE: Fixed, but I could do with a review on https://github.com/openfisca/openfisca-parsers/pull/11