Merge pull request #129 from clbe/master

Removed unused variable
Fix imports
Add support for monthly values in compact legislation.
Repair build..._formula_couple partials.
Improve detection of errors and names of variables in test_jsons.
Rename period_from_anything to period.
wip
Ignore tags file
Update reform test according to reform API changes
Refactoring reform
build_*_formula use now entity_class_by_symbol
wip
Ignore tags file
Update reform test according to reform API changes
Refactoring reform
MErge reform and disable a test
Fix bug in test_jsons
Fix build_column_couple in base
Add support for periods.
Fix tests