+ercc: plotting number of molecules vs RPKM (not only concentration vs RPKM)
+added possibility for aggregating by stratum: expr_dhist, sample2ngenes
*API improvement: Read data in bin rather than in lib fcn: ercc, pca, expr_dhist, sampledist_heatmap
*exp_dhist: improved x-axis tick labelling
*get.meta: bugfixed coverage boxplots