Updated graphql-core url

Author: syrusakbary

README.md

@@ -1,7 +1,7 @@
 # Relay Library for GraphQL Python
 
 This is a library to allow the easy creation of Relay-compliant servers using
-the [GraphQL Python](https://github.com/dittos/graphqllib) reference implementation
+the [GraphQL Python](https://github.com/graphql-python/graphql-core) reference implementation
 of a GraphQL server.
 
 *Note: The code is a __exact__ port of the original [graphql-relay js implementation](https://github.com/graphql/graphql-relay-js)
@@ -16,11 +16,11 @@ A basic understanding of GraphQL and of the GraphQL Python implementation is nee
 to provide context for this library.
 
 An overview of GraphQL in general is available in the
-[README](https://github.com/dittos/graphqllib/blob/master/README.md) for the
-[Specification for GraphQL](https://github.com/dittos/graphqllib).
+[README](https://github.com/graphql-python/graphql-core/blob/master/README.md) for the
+[Specification for GraphQL](https://github.com/graphql-python/graphql-core).
 
 This library is designed to work with the 
-the [GraphQL Python](https://github.com/dittos/graphqllib) reference implementation
+the [GraphQL Python](https://github.com/graphql-python/graphql-core) reference implementation
 of a GraphQL server.
 
 An overview of the functionality that a Relay-compliant GraphQL server should
@@ -30,16 +30,16 @@ describes a simple set of examples that exist as [tests](tests) in this
 repository. A good way to get started with this repository is to walk through
 that documentation and the corresponding tests in this library together.
 
-## Using Relay Library for GraphQL Python (graphqllib)
+## Using Relay Library for GraphQL Python (graphql-core)
 
 Install Relay Library for GraphQL Python
 
 ```sh
-pip install git+https://github.com/dittos/graphqllib.git # Last version of graphqllib
+pip install graphql-core --pre # Last version of graphql-core
 pip install graphql-relay
 ```
 
-When building a schema for [GraphQL](https://github.com/dittos/graphqllib),
+When building a schema for [GraphQL](https://github.com/graphql-python/graphql-core),
 the provided library functions can be used to simplify the creation of Relay
 patterns.