Update postgres version in travis build (#54)

* Update postgres version in travis build to 11.6

this is the most recent posgres version available in RDS at the moment

.travis.yml

@@ -6,7 +6,7 @@ services:
 - postgresql
 - docker
 addons:
-  postgresql: '11.2'
+  postgresql: '11.6'
 go_import_path: github.com/makerdao/vulcanizedb
 before_install:
 - make installtools

db/schema.sql

@@ -2,8 +2,8 @@
 -- PostgreSQL database dump
 --
 
--- Dumped from database version 12.1
--- Dumped by pg_dump version 12.1
+-- Dumped from database version 11.6
+-- Dumped by pg_dump version 11.6
 
 SET statement_timeout = 0;
 SET lock_timeout = 0;
@@ -32,7 +32,7 @@ $$;
 
 SET default_tablespace = '';
 
-SET default_table_access_method = heap;
+SET default_with_oids = false;
 
 --
 -- Name: addresses; Type: TABLE; Schema: public; Owner: -
@@ -662,7 +662,7 @@ CREATE INDEX transactions_header ON public.transactions USING btree (header_id);
 -- Name: headers header_updated; Type: TRIGGER; Schema: public; Owner: -
 --
 
-CREATE TRIGGER header_updated BEFORE UPDATE ON public.headers FOR EACH ROW EXECUTE FUNCTION public.set_header_updated();
+CREATE TRIGGER header_updated BEFORE UPDATE ON public.headers FOR EACH ROW EXECUTE PROCEDURE public.set_header_updated();
 
 
 --