removed a few unnecessary asterisks in doc.go
removed a few unnecessary asterisks in doc.go

evanphx/levigo,influxdata/hyperleveldb-go,influxdb/hyperleveldb-go,chanxuehong/goleveldb,alberts/gorocks,jmhodges/levigo_leveldb_1.4,influxdb/levigo,mikefaille/rocksdb-go,dckit/rocksdb,influxdata/rocksdb,elijahandrews/levigo,DanielMorsing/rocksdb,influxdb/rocksdb,jmhodges/levigo