Hot reload not triggered if package is installed by CNPM

[bruceCzK]

Version

3.0.1

Node and OS info

Node 8.11.4 / cnpm 6.0.0 / npm 6.2.0 / MacOS 10.13.6 and Windows 10

Steps to reproduce

$ vue create .
# use the default setting
$ rm -rf node_modules
$ cnpm install
$ npm run serve

What is expected?

Hot reload triggered after file been changed

What is actually happening?

While recompiling triggered correctly, the page isn't automaticly reload. Maybe there's an issue about package dependencies.

[haoqunjiang]

See: #1559