Swap and Paging: use kern.memorystatus_vm_pressure_level

[loopway]

I had frequent notifications of vm.memory_pressure being above 0 - yet no apparent issues because of it. I propose to use kern.memorystatus_vm_pressure_level which is available in OS X 10.9+ instead of vm.memory_pressure - as described in referenced link https://newosxbook.com/articles/MemoryPressure.html (information was probably added after you've created your check). This would also align with the information displayed in Activity Monitor.app.