Block categorization (#110)

* Add block categorization (is_final=)

* Add godo task for vulcanizeDB (Example of how everything could work together)

* Add unique constraint on block_number and node

* Add index on block_id for transactions_table

* Add node_id index on blocks table

* Sort transactions returned from FindBlock by tx_hash

* lowercase tx_to, tx_from like etherscan

pkg/history/populate_blocks_test.go

@@ -100,4 +100,14 @@ var _ = Describe("Populating blocks", func() {
 		Expect(window.Size()).To(Equal(2))
 	})
 
+	It("returns the number of largest block", func() {
+		blockchain := fakes.NewBlockchainWithBlocks([]core.Block{
+			{Number: 1},
+			{Number: 2},
+			{Number: 3},
+		})
+		maxBlockNumber := blockchain.LastBlock()
+
+		Expect(maxBlockNumber.Int64()).To(Equal(int64(3)))
+	})
 })