Added append command.
Added append command.

Closes #4

NoellyB76/try.redis,badboy/try.redis,badboy/try.redis,PradheepShrinivasan/try.redis,supasate/try.redis,supasate/try.redis,supasate/try.redis,badboy/try.redis,NoellyB76/try.redis,PradheepShrinivasan/try.redis,PradheepShrinivasan/try.redis,NoellyB76/try.redis