v0.5.2

• Added introspection-based schema materializer (#21). This feature has a lot of potential for clint-side tools, testing, mocking,
  creating facade GraphQL servers, etc.

  Here is simple example of how you can use this feature (Using circe in this particular example):

  import io.circe._
  import sangria.marshalling.circe._
  
  val introspectionResults: Json = ??? // coming from other server or file
  val clientSchema: Schema[Unit, Unit] = 
    Schema.buildFromIntrospection(introspectionResults)  

  It takes a results of full introspection query (loaded from the server, file, etc.) and recreates the schema definition with stubs for
  resolve methods. You can customize a lot of aspects of materialization by providing custom MaterializationLogic implementation
  (you can also extend DefaultMaterializationLogic class). This means that you can, for instance, plug in some generic field resolution logic (resolveField method) or
  provide generic logic for custom scalars (coerceScalar* methods). Without these customisations schema only would be able to execute introspection queries.

  By default, default values (for input object fields and arguments) would be ignored because it's just a string as far as introspection API is concerned. However you can enable default value
  support if you know the format of the default values (in many cases it would be JSON). There is even a helper function for this:

  import spray.json._
  import sangria.marshalling.sprayJson._
  
  val clientSchema: Schema[Unit, Unit] = 
    Schema.buildFromIntrospection(introspectionResults,
      MaterializationLogic.withDefaultValues[Unit, JsValue])

  This will inform schema materializer that default values are serialized as JSON and that spray-json should be used to work with them (please note, that
  circe does not have a built-in JSON parsing support, so it can't be used out-of-the-box here. On the other hand, it's pretty easy to add support for particular circe
  parser by defining an implicit instance of InputParser type class).

• SchemaRenderer.renderSchema is now able to render Schema objects and only introspection results (#114). This can be useful if you already
  have schema in memory and don't want to execute an introspection query against the schema in order to render it.

• Query validation rule: Unique variable names (#112)

• Add suggested types to incorrect field message (#111)

• Introspection result now has a parser which deserializes a JSON (or any other format) to a set of case classes. This may simplify client-side tools that work with introspection queries.
  Please use sangria.introspection.IntrospectionParser.parse to parse an introspection query results.

• Introduced InputParser type class in order provide optional support for default value parsing in schema materialization.

• Updated descriptions of a scalar values

• Updated dependencies

• Minor improvements