[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.
For this place, it's a bit complicated, because for historical reason, we want to let our node-acs-sdk to support passed-in request and response. Like [an example here (A Node.ACS app)](https://github.com/realpaul/acs-node-sdk/blob/4b2ce65701a5bd0486be8b8540492b2eab1b15e5/examples/over_nodeacs/controllers/application.js#L15-L22), sometimes customer use acs-node-sdk in our Node.ACS, and just be a broker. We will get all user parameters like username, password from request.body (request.query), then making a new request to ACS API. After getting response, we will pass it to response provided by Node.ACS. If there is any cookie got from response from ACS API, we will need to set to response from Node.ACS.
So for this place, I just want user passed request to be the main request body passing to ACS API. For reqBody, mostly it will contain ACS app key and other information like pre-production entry point for example, so it will be not empty.

Do you think I can use:
```
reqBody = _.merge(reqBody || {}, restOptions.req.query || {}, restOptions.req.body);
```
since reqBody is usually not empty?