message: Fix GraphQLCache test
  Not sure why, but looks like commit
  stripped out the MockWatchmanClient functionality, and because we
  weren't running the tests in CI, we didn't notice.
diff: import {expect} from 'chai';
  import {GraphQLSchema} from 'graphql/type';
  import {parse} from 'graphql/language';
  +import {getGraphQLConfig} from 'graphql-language-service-config';
  import {beforeEach, describe, it} from 'mocha';
  +import {join} from 'path';
  -import {getGraphQLCache} from '../GraphQLCache';
  +import {GraphQLCache} from '../GraphQLCache';
  +import MockWatchmanClient from '../__mocks__/MockWatchmanClient';
  describe('GraphQLCache', () => {
  let cache;
  let config;
  beforeEach(async () => {
  - cache = await getGraphQLCache(__dirname);
  + const watchmanClient = new MockWatchmanClient();
  + const configDir = __dirname;
  + const graphQLRC = await getGraphQLConfig(configDir);
  + cache = new GraphQLCache(configDir, graphQLRC, watchmanClient);
  config = cache.getGraphQLConfig();
  });
  