Add transformers for Cat file events

- transform logs from 3 implementations of file on the Cat contract

pkg/geth/blockchain.go

@@ -1,6 +1,7 @@
 package geth
 
 import (
+	"errors"
 	"math/big"
 
 	"github.com/ethereum/go-ethereum"
@@ -11,7 +12,6 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/vulcanize/vulcanizedb/pkg/core"
 	vulcCommon "github.com/vulcanize/vulcanizedb/pkg/geth/converters/common"
-	"errors"
 )
 
 var ErrEmptyHeader = errors.New("empty header returned over RPC")