Added a help file for the mergesort proficiency exercise
Added a help file for the mergesort proficiency exercise

hosamshahin/OpenDSA,hosamshahin/OpenDSA,hosamshahin/OpenDSA,RJFreund/OpenDSA,RJFreund/OpenDSA,RJFreund/OpenDSA,hosamshahin/OpenDSA,hosamshahin/OpenDSA,hosamshahin/OpenDSA,RJFreund/OpenDSA,RJFreund/OpenDSA,hosamshahin/OpenDSA,hosamshahin/OpenDSA,RJFreund/OpenDSA,hosamshahin/OpenDSA,RJFreund/OpenDSA,RJFreund/OpenDSA