Use --stretch instead of --maximize

[sihoang]

My screen is 1920 x 1080 and the --maximize flag does not use all my screen real estate. I think it'd look much better with --stretch. Are you open for PR to change this default behaviour?

[marcespie]

I'm not open to changing the default. I disagree with you on that one. I can add an option so that the script can use --stretch.

In general, adding "trim boxes" for files that do not fit well on 16:10 is a good idea.

Please look up my other project (aspect-crop) which is designed to figure out "trim boxes" ;)

[sihoang]

adding an option to use --stretch is much appreciated