Openfisca-extension-template

* Technical change
* Details:
- Adapt to OpenFisca Core v25
- Change the syntax of OpenFisca YAML tests

For instance, a test that was using the `input_variables` and the `output_variables` keywords like:

yaml
- name: Basic income
period: 2016-12
input_variables:
salary: 1200
output_variables:
basic_income: 600


becomes:

yaml
- name: Basic income
period: 2016-12
input:
salary: 1200
output:
basic_income: 600


A test that was fully specifying its entities like:

yaml
- name: "A couple with 2 children gets 200€"
period: 2016-01
households:
parents: ["parent1", "parent2"]
children: ["child1", "child2"]
persons:
- id: "parent1"
age: 35
- id: "parent2"
age: 35
- id: "child1"
age: 8
- id: "child2"
age: 4
output_variables:
local_town_child_allowance: 200


becomes:

yaml
- name: "A couple with 2 children gets 200€"
period: 2016-01
input:
households:
household:
parents: ["parent1", "parent2"]
children: ["child1", "child2"]
persons:
parent1:
age: 35
parent2:
age: 35
child1:
age: 8
child2:
age: 4
output:
local_town_child_allowance: 200

* Technical change
* Details:
- Tests library against its packaged version
- By doing so, we prevent some hideous bugs

_Note: the 1.1.5 version has been unpublished as it was used for test analysis_

* Add continuous deployment with CircleCI, triggered by a merge to `master` branch

* Declare package compatible with OpenFisca Country Template v3

* Technical improvement:
* Details:
- Adapt to version `21.0.0` of Openfisca-Core and version `2.1.0` of Country-Template

* Technical improvement:
* Details:
- Adapt to version `20.0.0` of Openfisca-Core and version `1.4.0` of Country-Template