v4.3.2 - GraphiQL Explorer

The lovely folks over at OneGraph sent a PR to integrate their GraphiQL Explorer into PostGraphile — this awesome feature really helps users get started with GraphQL. Make sure you're using --enhance-graphiql to use it! #981

Additionally @mlipscombe discovered an issue where your PgPool could become exhausted if an enough errors were thrown on COMMIT, and sent over a PR to fix: #978