math.MaxInt64 represents 8 exabytes, which is a good limit for memory.
Also, this is the type used by Docker, so it's not possible to get any
value bigger than math.MaxInt64 as memory limit (both ram and swap) on a
Docker container.

Relevant discussion at #589 (more precisely,
https://github.com/GoogleCloudPlatform/kubernetes/pull/589#issuecomment-50640605).