travis: Use py.test as test runner for unit tests.
travis: Use py.test as test runner for unit tests.

benthomasson/behave,Abdoctor/behave,Gimpneek/behave,Gimpneek/behave,jenisys/behave,jenisys/behave,benthomasson/behave,Gimpneek/behave,Abdoctor/behave