Time Zone information in TimeInfo

[Zameer Manji]

Hey,

I noticed there is a TODO on the TimeInfo for adding Time Zone information.
```
/**
 * Represents time since the epoch, in nanoseconds.
 */
message TimeInfo {
  required int64 nanoseconds = 1;

  // TODO(josephw): Add time zone information, if necessary.
}
```

Since there is no TZ information attached the timestamp, should frameworks
assume that the Mesos Master system TZ is the same as the framework TZ?
That is what I'm thinking of doing, but I'm not sure what was the intention
of the authors of the API.

Also, would it be possible to attach TZ information? It would make
understanding the TimeInfo much easier when it is received by the framework.

-- 
Zameer Manji