Add CLI flag to to reload gulp on gulpfile change

[doot0]

While there are a couple of workarounds for this floating around (see @tilap's example) having this feature baked in and accessible via flag would be pretty sweet.

[timothyis]

+1

[phated]

I think that this is better handled by external tools like nodemon or pm2

[timothyis]

@phated I believe this issue is the result of a suggestion by @contra saying that gulp could probably use a flag to watch for changes within the gulpfile itself. It's probably worth a thought at least, I think a few people would like this.

[phated]

Sure, but we always defer to external libraries when they do things better. We've already added lots of flags and the more we add, the more we clash with end users flags. I personally use a --watch flag inside my gulpfiles so I wouldn't want to take over that flag in the CLI