Add arriba to the RNA-seq tests.
Add arriba to the RNA-seq tests.

a113n/bcbio-nextgen,vladsaveliev/bcbio-nextgen,chapmanb/bcbio-nextgen,a113n/bcbio-nextgen,vladsaveliev/bcbio-nextgen,vladsaveliev/bcbio-nextgen,lbeltrame/bcbio-nextgen,chapmanb/bcbio-nextgen,chapmanb/bcbio-nextgen,lbeltrame/bcbio-nextgen,lbeltrame/bcbio-nextgen,a113n/bcbio-nextgen