JBrowse 1.16.6

Minor improvements

• Add name regularization for drosophila style chromsome naming so that
  2L maps to chr2L and vice versa (@scottcain)

• Add ability to index names in a BEDTabix file, enabled by default.
  Thanks to @billzt for the idea and implementation (pull #1393)

Bug fixes

• Fix the side scrolling on Mac misbehaving and triggering the browser's
  back action (a bug that existed only in 1.16.5). Thanks to @nathandunn
  for debugging (issue #1397)