add DB#size. surely there's a better way?
add DB#size. surely there's a better way?

wmorgan/leveldb-ruby,wmorgan/leveldb-ruby,wmorgan/leveldb-ruby,wmorgan/leveldb-ruby,assispedro/leveldb-ruby,assispedro/leveldb-ruby,assispedro/leveldb-ruby,assispedro/leveldb-ruby