[Conversation] Date deserialization

[boazdavid]

When I use curl to get workspaces
https://gateway.watsonplatform.net/conversation/api/v1/workspaces/?version=2017-02-03
I get the dates in this format:
"created": "2017-04-23T19:09:46.712Z"
which is UTC.

But when using the SDK, the date is: Sun Apr 23 19:09:46 IDT 2017. in my time zone (Israel, UTC +3).
Seems that the SDK does not understand the Z (UTC) syntax

see also #625