webhtml: reenable sort option for flamegraphs (#491)

This sorts flamegraph elements lexographiaclly such that two similar
profiles can be compared side-by-side to eyeball differences in
flamegraph profile shapes and sizes.

internal/driver/webhtml.go

       .transitionDuration(750)
       .transitionEase(d3.easeCubic)
       .inverted(true)
+      .sort(true)
       .title('')
       .tooltip(false)
       .details(document.getElementById('flamegraphdetails'));