The belated merges release

• upgrade jsonwebtoken to work around security issue in dependency (if this breaks your app you need to submit an issue so we have better tests)
• duck-typing pg in more places
• add experimental support for .postgraphilerc.js
• if no connection string is specified, connect via standard envvar DATABASE_URL before falling back on postgresql envvars (⚠️ if you already have DATABASE_URL available in your environment and you don't use the connection string option then ensure this does what you expect! ⚠️ )
• add support for PGUSER and PGPASSWORD envvars
• doc tweaks

Thanks to everyone who has been patient about me merging their pull requests!

Anyone using postgraphql@next - please switch to using postgraphile as I will not be keeping postgraphql@next up to date soon.