Add the cartodb extension as a dependency

It will be handy to have it available for SQL-implemented functions

pg/test/0.0.1/sql/01_install_test.sql

@@ -1,6 +1,7 @@
 -- Install dependencies
 CREATE EXTENSION plpythonu;
 CREATE EXTENSION postgis;
+CREATE EXTENSION cartodb;
 
 -- Install the extension
 CREATE EXTENSION crankshaft;