There's still some work to do to make this work on Linux and support 
switching between notification back-ends.

It was actually dead code and is screwing up V8 startup snapshots.

Need to figure out what to do with this for the long-term.

The logic is pretty complex and I don't want to take the time to 
integrate @atom/notify with it. I left a bunch of stuff commented out in 
this commit just in case these changes break the build. I'll do another 
pass to delete commented code once we go green.

I experimented with just reloading the Window, but ran into problems. 
I'm also worried about a situation where there are multiple windows. 
Since this setting should be changed rarely, I think prompting for a 
restart is an expedient solution.

I think that the notify subprocess might be holding a lock on the 
watched directory on Windows.

This will surface these errors to users and to our exception reporting 
infrastructure to ensure we get feedback on the new backend in the wild.

…safe"

This reverts commit 6da489e.

This commit was messing up the V8 startup snapshot.

This avoids problems with assertions that involve paths inside the temp 
folder.