Add missing dependency on DateTime::Format::Pg

TDBIC fails t/09-test-postgresql.t if DateTime::Format::Pg is not installed, b/c TDBIC::Example::Schema requires it for the TimeStamp and InflateColumn::DateTime components. I guess it should technically be a test_requires, but I figure it's common enough to merit a regular dependency.  Thank you for your time and efforts and have a great New Year!

Cheers,
Fitz