Refactor database drivers

README.md

 ```
 $ wget https://phar.phpunit.de/phpunit.phar
 $ php phpunit.phar tests/tests.php
-PHPUnit 4.7.3 by Sebastian Bergmann and contributors.
+PHPUnit 5.1.3 by Sebastian Bergmann and contributors.
 
-...................
+.....................................                             37 / 37 (100%)
 
-Time: 464 ms, Memory: 12.00Mb
+Time: 433 ms, Memory: 11.00Mb
 
-OK (19 tests, 39 assertions)
+OK (37 tests, 61 assertions)
 $
 ```
 
 ```
 $ wget https://phar.phpunit.de/phpunit.phar
 $ php phpunit.phar tests/tests.php
-PHPUnit 4.7.3 by Sebastian Bergmann and contributors.
+PHPUnit 5.1.3 by Sebastian Bergmann and contributors.
 
-......................
+.....................................                             37 / 37 (100%)
 
-Time: 894 ms, Memory: 2.75Mb
+Time: 856 ms, Memory: 11.25Mb
 
-OK (22 tests, 42 assertions)
+OK (37 tests, 61 assertions)
 $
 ```
 

tests/blog_postgresql.sql

 SET check_function_bodies = false;
 SET client_min_messages = warning;
 
---
---
-
-CREATE EXTENSION IF NOT EXISTS plpgsql WITH SCHEMA pg_catalog;
-
-
---
---
-
-COMMENT ON EXTENSION plpgsql IS 'PL/pgSQL procedural language';
-
-
 SET search_path = public, pg_catalog;
 
 SET default_tablespace = '';
 );
 
 
-ALTER TABLE public.categories OWNER TO postgres;
-
 --
 -- Name: comments; Type: TABLE; Schema: public; Owner: postgres; Tablespace:
 --
 );
 
 
-ALTER TABLE public.comments OWNER TO postgres;
-
 --
 -- Name: post_tags; Type: TABLE; Schema: public; Owner: postgres; Tablespace:
 --
 );
 
 
-ALTER TABLE public.post_tags OWNER TO postgres;
-
 --
 -- Name: posts; Type: TABLE; Schema: public; Owner: postgres; Tablespace:
 --
 );
 
 
-ALTER TABLE public.posts OWNER TO postgres;
-
 --
 -- Name: tags; Type: TABLE; Schema: public; Owner: postgres; Tablespace:
 --
 );
 
 
-ALTER TABLE public.tags OWNER TO postgres;
-
 --
 -- Name: users; Type: TABLE; Schema: public; Owner: postgres; Tablespace:
 --
 );
 
 
-ALTER TABLE public.users OWNER TO postgres;
-
 --
 -- Data for Name: categories; Type: TABLE DATA; Schema: public; Owner: postgres
 --
     ADD CONSTRAINT posts_user_id_fkey FOREIGN KEY (user_id) REFERENCES users(id);
 
 
---
---
-
-REVOKE ALL ON SCHEMA public FROM PUBLIC;
-REVOKE ALL ON SCHEMA public FROM postgres;
-GRANT ALL ON SCHEMA public TO postgres;
-GRANT ALL ON SCHEMA public TO PUBLIC;
-
-
 --
 -- PostgreSQL database dump complete
 --
-