node-diskusage issue

[Shybert]

jduncanator/node-diskusage#32

I was able to build xelib on its own with Node 10, but not together with zEdit, even when I had updated the "diskusage" dependency. z-edit/xelib#4

[matortheeternal]

I currently build zEdit with Node 8.x. If node-diskusage still works with Node 8.x with the update then I will accept the PR.

[Shybert]

Works fine for me on my PC with Node 8.12.0.

[jduncanator]

node-diskusage should work with everything all the way back to Node v0.10. Theoretically it should work with v0.8, but I don't test this and can't promise it will always work in v0.8.