db: add delete/2
db: add match/2
db: add eunit tests
db: add my_db eunit tests
my_db: add start/0 and stop/0
my_db: add init/0
my_db: implement internal message handling functions
my_db: use refs for call messages, nothing for casts
my_db: add external API
db: add records to db
db: remove all types coz records
db: use records
db: use records in a header
db: use ETS
mutex: a basic semaphore
mutex: trap exits for more fun
mutex: add catch, maybe this is not right