Gene spans track from maker2jbrowse error

[cmdcolin]

From http://jbrowse.org/demos/yeast_pilon_jbrowse_datadir.tar.gz

[cmdcolin]

Appears to be related to the use of the --noSubfeatures flag

Results in attributes named "start" which has a stringified number on the feature so feature.get('start') returns a string

[cmdcolin]

@domenico-simone removing --noSubfeatures line from the bin/maker2jbrowse script can fix for now. See #1554 PR for a simple fix

Would need another investigation to completely figure out why noSubfeatures is non functional

[cmdcolin]

could also git bisect to find when if ever this was working :)