fix(pipes): bug when "resolver" is not set

fix(datetimes): try to fix the timezones problem

fix(error handling): always returns 200

Same reasoning as
graphql/express-graphql#116 (comment)

Hope it doesn't break #25

Merge pull request #34 from lorado/bug/33

allow pipe definition with params

fix(style): fix phpstan errors

fix(relations): fix bug with overriden Model relations

also refactor StoreTransformer Relations management

Merge pull request #27 from lorado/bug/26

Fixing n+1 relations problem

Merge pull request #30 from studio-net/f-laravel57

Laravel 5.7

adds & fixes tests

updates Readme