Replace fs.watch with chokidar

[bonanitech]

This excerpt from the chokidar documentation explains the reasoning behind this change.

Why?

Node.js fs.watch:

• Doesn't report filenames on MacOS.
• Doesn't report events at all when using editors like Sublime on MacOS.
• Often reports events twice.
• Emits most changes as rename.
• Does not provide an easy way to recursively watch file trees.
• Does not support recursive watching on Linux.

Node.js fs.watchFile:

• Almost as bad at event handling.
• Also does not provide any recursive watching.
• Results in high CPU utilization.

Chokidar resolves these problems.