Stackable Box 4 slipt

This is a remix of Gushie's http://www.thingiverse.com/thing:447213, which is a remix of 1986breeze's http://www.thingiverse.com/thing:234669, which is a remix of martinhering's http://www.thingiverse.com/thing:177814

I reinforced the front lip, and adjusted the design to increase stability when stacking. The result should be a drastic improvement to stackability and no significant increase in material usage or print time. The design is fully backwards compatible with both Gushie and 1986breeze's versions (in that they'll stack).

I also add a divider to have 4 box where put the things