gene_level_changes highest alteration

[BastienNguyen]

In gene_level_changes.R

seg = seg[which.max(start-end)], # this selects the segment which represents the larger region

it would be nice to add an option to select the segment with the highest absolute log2(cn). The rational being that sometimes a particular exon is deleted but not the whole gene. So by using the larger region, it might mask the true deletion.