removed salary_rule record because it makes hr_payroll_account test fail
Reactivate UNIT_TEST
Addedintall wkhtmltopdf in .travis.yml because it is a depedency for module account_financial_report_webkit
Changed version of wkhtmltopdf to install on travis
Merge pull request #28 from savoirfairelinux/7.0-ddufresne-fix_salary_rules

[IMP] Remove salary_rule record because it makes hr_payroll_account test fail