Handle redirect responses for SUBSCRIBE calls

[cruhland]

As described in the "Master detection" section of the Scheduler HTTP API docs (bottom of page), SUBSCRIBE requests will receive a 307 response status code (Temporary Redirect) if sent to a non-leading Mesos master. The response will include a Location header with the host and port of the leading master.

The MesosSchedulerClient should handle this possibility automatically, for user convenience.

[BenWhitehead]

Duplicate of #18