Change tests to use postgres-json-schema instead of hjsonschema.

Embeds https://github.com/gavinwahl/postgres-json-schema.

stack.yaml

@@ -2,8 +2,6 @@ resolver: lts-9.6
 extra-deps:
   - configurator-ng-0.0.0.1
   - critbit-0.2.0.0
-  - hjsonpointer-1.1.1
-  - hjsonschema-1.5.0.1
   - Ranged-sets-0.3.0
   - protolude-0.2.2
   - hasql-1.3
@@ -18,6 +16,3 @@ ghc-options:
   postgrest: -O2 -Werror -Wall -fwarn-identities -fno-warn-redundant-constraints
 nix:
   shell-file: shell.nix
-# only added because of hjsonschema conflict with http-types
-# once hjsonschema upper bounding on http-types is solved it can be removed
-allow-newer: true