travis: Add required packages.
travis: Add required packages.

==== FAILING TESTS

AlexIljin/factor,bpollack/factor,AlexIljin/factor,mrjbq7/factor,AlexIljin/factor,AlexIljin/factor,tgunr/factor,factor/factor,bpollack/factor,bpollack/factor,mrjbq7/factor,tgunr/factor,bpollack/factor,factor/factor,bpollack/factor,bpollack/factor,factor/factor,factor/factor,tgunr/factor,mrjbq7/factor,mrjbq7/factor,mrjbq7/factor,AlexIljin/factor,AlexIljin/factor,mrjbq7/factor,bpollack/factor,AlexIljin/factor,factor/factor,tgunr/factor,tgunr/factor,tgunr/factor,factor/factor