This change:
* gives us the flexibility of managing node from pull-request to pull-request. It'll be a huge lift to folks that want to test out node upgrades like @bjacobel or @andy-armstrong
* Sets us up for a port to Xenial, which will be accomplished in part by using nodeenv for managing the node environment. See a companion PR on the configuration repo for edxapp: edx/configuration#3444

This pull request does not:
* Attempt to solve any stability issues in builds related to node.
* Make node installs any faster
* Create any caching infrastructure to speed up node installs. They will be approximately as fast as they were before. Downloading the node bits build-to-build adds about 3 seconds, which is worth it for the added flexibility.

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.

Updated README with greater detail

updated README

PR update

PR update (squash)

README updated with minor PR updates

Script to collect data on the xblock usage within the edx platform, This script uses the Course block API and returns CSV reports

Updates for Pep8 compliance

Fixed issues found while testing with greater datasets and found during report review

PR updates (Squash)

The Catalog model is unmanaged, meaning no corresponding table exists in the database. When dumpdata tries to dump this model, it chokes because there's no table to read from.