Fixes issue #8 by syncing (copy+paste) sails-disk

Fixes sails-memory issue #8 and, I think, https://github.com/balderdashy/waterline/issues/346

Looks like the sails-disk got updated for some changes whereas sails-memory didn't.

I more-or-less copy+pasted the apparently-relevant changes from sails-disk to sails-memory
et voila, it passes the tests and also no longer causes problems in my own project.

I won't pretend to understand _why_ this works though :laughing: