Add receipts (#119)

* Conversion between Geth Receipt and core.Receipt

* Add receipt to DB

* Insert receipts with transactions

* Update Travis CI to use dep for dependencies

db/migrations/1514564898_create_receipts_table.down.sql

@@ -0,0 +1,2 @@
+DROP TABLE receipts;
+

db/migrations/1514564898_create_receipts_table.up.sql

@@ -0,0 +1,16 @@
+CREATE TABLE receipts
+(
+  id                  SERIAL PRIMARY KEY,
+  transaction_id      INTEGER NOT NULL,
+  contract_address    VARCHAR(42),
+  cumulative_gas_used NUMERIC,
+  gas_used            NUMERIC,
+  state_root          VARCHAR(66),
+  status              INTEGER,
+  tx_hash             VARCHAR(66),
+  CONSTRAINT transaction_fk FOREIGN KEY (transaction_id)
+  REFERENCES transactions (id)
+  ON DELETE CASCADE
+);
+
+

db/migrations/1514932205_add_transaction_id_index_to_receipts.down.sql

@@ -0,0 +1 @@
+DROP INDEX transaction_id_index;

db/migrations/1514932205_add_transaction_id_index_to_receipts.up.sql

@@ -0,0 +1 @@
+CREATE INDEX transaction_id_index ON receipts (transaction_id);