Rework core (version 0.3dev).
Add axes to simulations.
Remove X_AXES and remove obsolete and commented code.
Add options to new_single_entity_simulation.
Move tests in Travis configuration.
Correct test name.
Remove obsolete dependency.
Adding some cotisations patronales parameters
reworking test_brut_to_imposable
transition to new core methods
Still in transition
Transition finished for brut_to_imposable
Cleaning