Extends assert_near to date comparison

[benjello]

Technical changes

• Extends assert_near to date comparison

[benjello]

@sandcha : I do nt understand the test erros since it seems unrelated to my changes. any hints @sandcha ?

[sandcha]

Hi @benjello , As the error is thrown on this test:

def test_parameter_node():
        response = subject.get('/parameter/benefits')
...

and the last update of the openfisca/country-template#99 adds a openfisca_country_template/parameters/benefits/parenting_allowance.yaml, which comes with a minor update of the package, it looks like a test that is close to the implementation and that we can update to avoid this type of situation.

[benjello]

@sandcha : tests pass now ! You can review ;-)

[sandcha]

LGTM. Thx @benjello!
Please don't forget to update with a rebase and, in the best of all possible worlds, set the name of the PR as message for the merging commit :)

[sandcha]

Just a reminder: bump needed (+ only 2 #)