RNASeq: make SummarizedExperiment object.
RNASeq: make SummarizedExperiment object.

This is to prepare for a simpler version of bcbioRNASeq where the code
for the figures is more exposed and easy to modify.

lbeltrame/bcbio-nextgen,lbeltrame/bcbio-nextgen,lbeltrame/bcbio-nextgen