Canonical blocks (#108)

* Update Block w/ newest Block

* Add cascading delete to blocks and transactions tables

* Add handling for new conflicting blocks

* Command line version of sliding window n behind HEAD

integration_test/geth_blockchain_test.go

@@ -1,6 +1,9 @@
 package integration_test
 
 import (
+	"io/ioutil"
+	"log"
+
 	"github.com/8thlight/vulcanizedb/pkg/blockchain_listener"
 	"github.com/8thlight/vulcanizedb/pkg/config"
 	"github.com/8thlight/vulcanizedb/pkg/core"
@@ -10,6 +13,10 @@ import (
 	. "github.com/onsi/gomega"
 )
 
+func init() {
+	log.SetOutput(ioutil.Discard)
+}
+
 var _ = Describe("Reading from the Geth blockchain", func() {
 
 	var listener blockchain_listener.BlockchainListener