accoung example simulates account service by account-server. Using
account-client user can change balance of its account.  Please use two
terminals, one for server and one for client.

Compile the programs doing:
bash> make

Start server in first terminal:
bash> ./account-server

Start client in second terminal multiple times, depositing or
withdrawing money: 
bash> ./account-client +500 
bash> ./account-client -300






