*`apollo-server-core`: **breaking** gql is exported from gql-tag and ApolloServer requires a DocumentNode [PR#1146](https://github.com/apollographql/apollo-server/pull/1146)
*`apollo-server-core`: move query parse into runQuery and no longer accept GraphQL AST over the wire [PR#1097](https://github.com/apollographql/apollo-server/pull/1097)
*`apollo-server-core`: context creation can be async and errors are formatted to include error code [PR #1024](https://github.com/apollographql/apollo-server/pull/1024)
*`apollo-server-core`: add `mocks` parameter to the base constructor(applies to all variants) [PR#1017](https://github.com/apollographql/apollo-server/pull/1017)
*`apollo-server-core`: Remove printing of stack traces with `debug` option and include response in logging function[PR#1018](https://github.com/apollographql/apollo-server/pull/1018)