moment() -> _isUTC is false for offset returning -0

[mdemblani]

Description of the Issue and Steps to Reproduce:
On bootstraping the node application, when the timezone is set to UTC using the env variable as follows:
process.env.TZ = 'UTC';

The timezone is updated. MomentJS returns the date object in UTC Time. But inspecting the moment-date object closely shows that the flag _isUTC is set to false. On further inspection with the JS date object,

var d = new Date();
d.getTimezoneOffset();        //Returns 0

moment().utcOffset();          //Returns -0

Further checking it, if timezone is updated to 0 for moment object, everything works fine, but when it is -0, it does not.

Environment:

1. MomentJS - 2.14.1
2. Node - 6.2.2
3. Ubuntu - 16.04

Code to run before reporting

console.log( (new Date()).toString())
console.log((new Date()).toLocaleString())
console.log( (new Date()).getTimezoneOffset())
console.log( navigator.userAgent)
console.log(moment.version)

Output:

1. 'Sat Oct 22 2016 15:18:09 GMT+0000 (UTC)'
2. '10/22/2016, 3:18:25 PM'
3. 0
4. NA - Node.JS
   5.2.14.1

[icambron]

Confirmed in 2.15.1.

[icambron]

Fixed in #3523.