modify retrieveByteBufferFromRemoteMachine in TachyonFile.java according to new interface just like RemoteBlockInStream.java
add test case for TachyonFile
close the buffer after Assert
Merge pull request #349 from shimingfei/TachyonFileFix

modify retrieveByteBufferFromRemoteMachine in TachyonFile.java according to RemoteBlockInStream.java