I just installed Visual Studio 2017 and opened a solution I had been working in with Visual Studio 2015. It seems like everything works great except that the task runner explore
I found the NPM Task Runner extension in the Visual Studio Marketplace that fixed my problem. After installing it, the package.json file showed up in Task Runner Explorer.
Also, don't forget to set your system path to be the top priority for the External Web Tools by going into Options > External Web Tools and moving $(PATH) up the list. My npm scripts were failing until I did this as well.