TFS doesn't respect tachyon-ft scheme

Hi,

I added couple of tests (I'm not sure if You think that Powermock is good idea here, however I wanted to test that proper URI is passed to TachyonFS, since this is the responsibility of TFS#initialize method and I felt is a bit overkill to setup tachyon client/server here)

I also fix documentation there is a need to add some settings to SPARK_JAVA_OPTS in order setup to work. I have verified that one running spark shell on mesos cluster.