Improve build memory limits

[sarahcodes100]

Our builds are frequently failing because they hit the 4G memory limit on circle: Your build has exceeded the memory limit of 4G on 1 container. The results of this build are likely invalid. We have taken a snapshot of the memory usage at the time, which you can find in a build artifact named memory-usage.txt. The RSS column in this file shows the amount of memory used by each process, measured in kilobytes.

We should look at the memory-usage.txt and consider limiting the JVM's usage with _JAVA_OPTIONS: https://circleci.com/docs/1.0/oom/