v3.1.0b2

Third beta release of GraphQL-core 3.1, based on GraphQL.js v15.0.0rc2.

In addition to incorporating the latest changes from the master branch of GraphQL.js, this release also contains the following improvements:

• Increased performance by using a faster isawaitable() function (#54).
• Nodes and some other objects are now extensible and weak-referencable (#82).

We also renamed the repository on GitHub from graphql-python/graphql-core-next to graphql-python/graphql-core.

Contributors to this release were:

@Cito, @astronouth7303, @Hellzed and @qeternity

Thanks to everybody who contributed by sending bug reports or pull requests. Please continue to report any problems you find in this beta release, so that these can be fixed in the final v3.1 release.