Add StorageTier into Tachyon
fix some typo and format
small fix for getting block size
Fixed the userId changing issue [TACHYON-171]

The problem is that if a user opens a client connection and starts
writing a file, but finishes writing after a certain
timeout (user.master.client.timeout.ms), then the MasterClient will
close its connection before the file is written, then reconnect and get
a new userId, which will screw up the write.

I'm not quite sure why we automatically close the connection if it
hasn't been used for a while, as we aren't really wasting any resources
by keeping it open. This change removes the original heartbeat
mechanism, which tracks how recently the client has been used and closes
the connection automatically, with a heartbeat that pings the master to
check the connection, and closes the client only if it can't connect to
the master. Now on a long write (or any operation with the client that
takes longer than user.master.client.timeout.ms), we won't reconnect and
change the userId.
simplify code path of converting String to enum in StorageLevelAlias
Documentation fixes
Undid the changes to MasterClient retry logic
modify according to latest code style
fix lockblock bug in checkpoint thread in workerstorage
Remove logging impl from client jar
close the checkpoint file before moving it
Merge pull request #512 from shimingfei/lockBlockFix

fix lockblock bug in checkpoint thread
Add indentaion rule for checkstyle using Google Java style.
Merge pull request #515 from hsaputra/add_indent_checkstyle

Add indentation rule for checkstyle using Google Java style.
Added javadoc/source jar in build so publish will include them
update document for devs
use closer to close resources in TachyonFile
refact getFileStatus in TachyonFs
Fixed formatting issues
Merge pull request #518 from shimingfei/TachyonFileFix

use closer to close resources in TachyonFile