I've seen out of memory exceptions when trying
to run many parallel builds against the same Zinc
server during packaging. We should use the same
increased memory settings we use for Maven itself.

I tested this and confirmed that the Nailgun JVM
launched with higher memory.

Author: Patrick Wendell <patrick@databricks.com>

Closes #4643 from pwendell/zinc-memory and squashes the following commits:

717cfb0 [Patrick Wendell] SPARK-5856: Launch Zinc with larger memory options.