[NODEJS-1598] PoC of acs-node-sdk Rework

## Ticket Information
***JIRA Ticket***
https://jira.appcelerator.org/browse/NODEJS-1598

***Description***
This PR is about to raise a PoC of ACS Node SDK rework. It re-designs framework of acs-node-sdk, and supports multiple instances. It also provides a way to list all available ACS objects and methods including doc url for a good reference. Test framework with travis-ci is added too for a good and automatic test.

Since this is only a PoC, I only implemented ACS object "Users". If this way is towards to a good direction and passes code review, we will add all other ACS objects later.

## Get started
Please refer to readme file https://github.com/realpaul/acs-node-sdk/blob/NODEJS-1598_ReworkPoC/README.md for a general usage.
This shouldn't have `-node` in the name. See: https://www.npmjs.org/doc/files/package.json.html. It should really just be `acs`. This conflicts with the existing acs CLI, but really, that isn't a CLI for acs, it is a CLI for Node.ACS. I'd recommend we rename the acs CLI to (something like) `nodeacs` and call this module `acs`. We can still install a global `acs` command for backward compatibility. This works nicely from a version standpoint because we can simply release this SDK as `acs@2.0.0` and can still release the old acs as `nodeacs@1.0.17`.

cc @jhaynie, @mgoff, @baobeimm