pg8000 passing test/sql/test_types.py

Opened up two tests that now pass with pg8000. Also, rewrote two tests
to use actual tables rather than having a round trip in a single select
statement. This is necessary for pg8000 because it sends strings to the
server with type 'unknown' and lets the server work out the type.
PEP8 tidy of test/sql/test_types.py
Merge pull request #99 from tlocke/master

pg8000 passing test/sql/test_types.py