Attempt to fix circle.

- update to node 10
- set maxWorkers on unittests so they don't spawn so many that we run 
out of memory.
- set runInBand on integration tests. There's a weird interaction that 
makes the constumes test or tutorials test fail due to a page crash.

.circleci/config.yml

@@ -40,7 +40,7 @@ aliases:
         - v1-npm-
   - &defaults
     docker:
-      - image: circleci/node:8.16-browsers
+      - image: circleci/node:10-browsers
     working_directory: ~/repo
 
 jobs:
@@ -76,7 +76,7 @@ jobs:
           name: Unit
           environment:
               JEST_JUNIT_OUTPUT_DIR: test-results/unit
-          command: npm run test:unit -- --reporters="default" --reporters="jest-junit" --coverage --coverageReporters=text --coverageReporters=lcov
+          command: npm run test:unit -- --reporters="default" --reporters="jest-junit" --coverage --coverageReporters=text --coverageReporters=lcov --maxWorkers="2"
       - store_artifacts:
           path: coverage
       - store_test_results:
@@ -123,7 +123,7 @@ jobs:
               JEST_JUNIT_OUTPUT_DIR: test-results/integration
           command: |
             export TESTFILES=$(circleci tests glob "test/integration/*.test.js" | circleci tests split --split-by=timings)
-            $(npm bin)/jest ${TESTFILES} --reporters="default" --reporters="jest-junit"
+            $(npm bin)/jest ${TESTFILES} --reporters="default" --reporters="jest-junit" --runInBand
       - store_test_results:
           path: test-results
 
@@ -162,7 +162,7 @@ jobs:
           git config --global user.email $(git log --pretty=format:"%ae" -n1)
           git config --global user.name $(git log --pretty=format:"%an" -n1)
       - run: npm run deploy -- -e $CIRCLE_BRANCH
-      
+
 workflows:
   version: 2
   build-test-deploy: