support Ubuntu's bootstrap version string
support Ubuntu's bootstrap version string

bootstrap version strings like "debootstrap 1.0.67ubuntu0.2" before would generate the error: "/home/nuno/omap-image-builder/scripts/install_dependencies.sh: line 55: [: 67ubuntu0: integer expression expected"
robert-budde/omap-image-builder,robert-budde/omap-image-builder,jadonk/image-builder,RobertCNelson/omap-image-builder,jadonk/image-builder,miloh/image-builder,beagleboard/image-builder,beagleboard/image-builder,miloh/image-builder,RobertCNelson/omap-image-builder