Add Changes entry for numeric field default fix
initial batch_alter_table for ::Producer::PostgreSQL
test to demonstrate Pg diff failure with rename_table+rename_field
Clean up Pg batch alter test

- Only use Test::PostgreSQL if DBICTEST_PG_DSN isn't set
- Use sqlt_test_ prefix for tables we create
- Drop the tables we created on exit
- Use lives_ok for the SQL we're testing
Fix POD syntax for PODed-out code
Document producer_args in SQL::Translator::Diff
Fix argument documentation for preprocess_schema
Factor out calling of normal diff-production functions
Add Changes entry for Pg diff fix
[merge] Batch alter support for Pg and refactoring

Fixes #44