Run `npm ls` for npm 5+
Run `npm ls` for npm 5+

Starting with version 5, npm no longer displays dependency tree
when you run `npm install`.

In https://github.com/npm/npm/issues/17594, the npm team indicated
that there is no way to mimic the previous behavior with a single
command.

craigcitro/travis-build,andyli/travis-build,craigcitro/travis-build,andyli/travis-build