reuse cluster for TFsShellTest and made each test isolated
TachyonFSTest now uses a shared cluster to speed up test run times
Cut FileInStreamTest time in 1/3 by making cluster shared between tests
Cut RemoteBlockInStreamTest run time by 1/4th by reusing the cluster between runs
Changed LocalBlockInStreamTest to use local cluster, cutting the time to run in thirds
Refactored RemoteBlockInStream

The code was convoluted, so I cleaned it up. Also the readByteBuffer
code in TachyonFile was copying almost all the logic from
RemoteBlockInStream, so I just exposed the necessary methods in
RemoteBlockInStream for TachyonFile to call.
Fixed bug in RemoteBlockInStream

I had to seek to the beginning of the block when initializing the
checkpoint input stream.
configuration fix : conf pass down
Replaced usage of 'slave' to 'worker' in Tachyon deployments. Updated scripts in bin/ appropriately. Renamed 'slaves' files to 'workers'. Updated the docs.
Merge pull request #582 from abhirajbutala/tachyon-213

[TACHYON-213] Replaced usage of 'slave' to 'worker' in Tachyon deployments.
Merge pull request #559 from manugoyal/remote-read-code

Refactored RemoteBlockInStream
Merge hierarchy store into Tachyon - thrift change
Merge hierarchy store into Tachyon - non-thrift change
refactor promote block code, adding comments and format
remove DropAfterPromote and configuration change
clean code and some bug fix
try to get block information from worker when information from master is outdated
fix test cases for TachyonFS
heartbeat simplify thrift change
heartbeat simplify non-thrift change test OK