fix the failing spec with ruby-1.9.3-p327 version

The specs was passed previously with ruby-1.9.3-p194,
but not with ruby-1.9.3-p327 version.
After this modification the specs are passing.
[fix #49834805] Added header/footer to the label_printer
[fix #49834805] added specs for printing multiple label
Merge pull request #23 from ke4/49834805_create_a_script_to_print_a_barcode_with_a_printer

49834805 create a script to print a barcode with a printer