[DOC] Add Karol Brejna to contributors
[DOC] Add Karol Brejna to contributors

Author: manuzhang <owenzhang1990@gmail.com>

Closes #149 from manuzhang/doc.

manuzhang/incubator-gearpump,manuzhang/incubator-gearpump,manuzhang/incubator-gearpump,manuzhang/incubator-gearpump,manuzhang/incubator-gearpump