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

db/migrations/1513192766_add_cascade_delete_to_transactions.down.sql

@@ -0,0 +1,11 @@
+BEGIN;
+
+ALTER TABLE transactions
+  DROP CONSTRAINT blocks_fk;
+
+ALTER TABLE transactions
+  ADD CONSTRAINT fk_test
+FOREIGN KEY (block_id)
+REFERENCES blocks (id);
+
+COMMIT;

db/migrations/1513192766_add_cascade_delete_to_transactions.up.sql

@@ -0,0 +1,12 @@
+BEGIN;
+
+ALTER TABLE transactions
+  DROP CONSTRAINT fk_test;
+
+ALTER TABLE transactions
+  ADD CONSTRAINT blocks_fk
+FOREIGN KEY (block_id)
+REFERENCES blocks (id)
+ON DELETE CASCADE;
+
+COMMIT;

db/migrations/1513275969_add_cascade_delete_to_blocks.down.sql

@@ -0,0 +1,11 @@
+BEGIN;
+
+ALTER TABLE blocks
+  DROP CONSTRAINT node_fk;
+
+ALTER TABLE blocks
+  ADD CONSTRAINT node_fk
+FOREIGN KEY (node_id)
+REFERENCES nodes (id);
+
+COMMIT;

db/migrations/1513275969_add_cascade_delete_to_blocks.up.sql

@@ -0,0 +1,12 @@
+BEGIN;
+
+ALTER TABLE blocks
+  DROP CONSTRAINT node_fk;
+
+ALTER TABLE blocks
+  ADD CONSTRAINT node_fk
+FOREIGN KEY (node_id)
+REFERENCES nodes (id)
+ON DELETE CASCADE;
+
+COMMIT;