add in support for batched writes

implement batch ops for different datastore types

rename Transaction to Batch

Revert "add in support for batched writes"

add in benchmarks for put and batchput

move batching into separate interface

address concerns from PR

regrab old code

datastore.go

@@ -100,40 +100,6 @@ func (d *datastore) Query(q dsq.Query) (dsq.Results, error) {
 	return qr, nil
 }
 
-type ldbBatch struct {
-	b *leveldb.Batch
-	d *datastore
-}
-
-func (d *datastore) StartBatchOp() ds.Transaction {
-	return &ldbBatch{
-		b: new(leveldb.Batch),
-		d: d,
-	}
-}
-
-func (b *ldbBatch) Put(key ds.Key, val interface{}) error {
-	v, ok := val.([]byte)
-	if !ok {
-		return ds.ErrInvalidType
-	}
-	b.b.Put(key.Bytes(), v) // #dealwithit
-	return nil
-}
-
-func (b *ldbBatch) Delete(key ds.Key) error {
-	b.b.Delete(key.Bytes())
-	return nil
-}
-
-func (b *ldbBatch) Commit() error {
-	opts := &opt.WriteOptions{Sync: true}
-	if err := b.d.DB.Write(b.b, opts); err != nil {
-		return err
-	}
-	return nil
-}
-
 func (d *datastore) runQuery(worker goprocess.Process, qrb *dsq.ResultBuilder) {
 
 	var rnge *util.Range