bugfix with dirPath

[Gaurav0]

trafficstars

This is a fix for the error:

TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received null

I am getting in CI of ember-fetch. Tracing the error, npm install failed when creating a fresh app due to use of a dirPath outside the project.

It also cleans up the use of bower, since this project already doesn't work with bower and ember < 3 anyway.