Update NKDCode128Barcode.m

Check digit calculation is a modulo 103 checksum, but _encodeNumberPair only has switch-case from 0 to 99.
Check character encoding fails when checksum value is 100, 101 or 102.

Fix : Added bar/space pattern for values 100, 101 and 102
Merge pull request #10 from jasonkhonm/patch-1

Update NKDCode128Barcode.m