Fix readRawBlock: a forgotten BufferPool Put (#168)

diff --git a/leveldb/table/reader.go b/leveldb/table/reader.go
index c5be420..16cfbaa 100644
--- a/leveldb/table/reader.go
+++ b/leveldb/table/reader.go
@@ -581,6 +581,7 @@
 	case blockTypeSnappyCompression:
 		decLen, err := snappy.DecodedLen(data[:bh.length])
 		if err != nil {
+			r.bpool.Put(data)
 			return nil, r.newErrCorruptedBH(bh, err.Error())
 		}
 		decData := r.bpool.Get(decLen)