Also, help with an echo.

Some Jenkins builds are erroring when attempting to set up the
npm environment with the error:

`npm ERR! cb() never called!`

Although it could point to a couple of different things, it is more classically
a sign of a dirty npm environment cache. Cleaning the cache at the start
of any given Jenkins job (which are sourced through this file) should
alleviate the problem.

Sass compilation is no longer dependent on Ruby, so we are
removing its dependencies.

The jenkins-common script is the better place for this particular setup, since that
script is doing similar setup steps to prepare the environment for running
various tests/subsequent scripts. This also will resolve downstream processes,
such as our jenkins AMI builder (for jenkins-worker images).