Fixed 2 programming errors in hr modules that make tests crash on other modules
Simplified the change on hr_job_categories
Added unit tests
Added store parameter on job_id on model hr_contract in module hr_contract_multi_jobs and added tests for it.
Changed assertTrue for assertEqual
Merge pull request #54 from savoirfairelinux/7.0-ddufresne-fix_hr_modules

Fix programming errors in hr modules