Improve pretty-print spacing on multi-column rows

Minor change to improve spacing when pretty-printing multi-column rows.

Instead of:

user=> (pm (matrix [[3 4 5][2 4 6]]))
[[3.000 4.0005.000]
 [2.000 4.0006.000]]
nil

With change:

user=> (pm (matrix [[3 4 5][2 4 6]]))
[[3.000 4.000 5.000]
 [2.000 4.000 6.000]]
nil


Signed-off-by: John Poplett <john.poplett@acm.com>