Add Drip drip transformer

db/migrations/1536710319_create_drip_drip_table.down.sql

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+DROP TABLE maker.drip_drip;

db/migrations/1536710319_create_drip_drip_table.up.sql

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+CREATE TABLE maker.drip_drip (
+  id            SERIAL PRIMARY KEY,
+  header_id     INTEGER NOT NULL REFERENCES headers (id) ON DELETE CASCADE,
+  ilk           TEXT,
+	tx_idx        INTEGER NOT NUll,
+  raw_log       JSONB,
+  UNIQUE (header_id, tx_idx)
+);