Help Message

`tl copy` returns `   -b BBOX, --bounds BBOX        WGS84 bounding box  [-180,-85.0511,180,85.0511]` which is misleading. The correct syntax is given in the README.md file.

`   -b BBOX, --bounds BBOX        WGS84 bounding box  ["-180 -85.0511 180 85.0511"]` would be less confusing.