[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 tough-cookie, it is required by [node module 'request'](https://github.com/mikeal/request). For this part, as [commented above](https://github.com/realpaul/acs-node-sdk/pull/2#discussion_r17467423), we want to write cookie back to provided response, if provided response is there. Because this is another request raised from user, not request we make to ACS API, we cannot set cookie directly. Moreover, we don't know if user uses expressjs or not, we cannot just use `restOptions.res.cookie=xxxx` directly.
I ever tried to use tough-cookie to do this but got failed. This is the way I have tested and can work well inner Node.ACS, so I kept and used this. Also I removed variable of require('tough-cookie'), since it is not needed in our code, but just leave it in package.json for node module 'request'.