Add check for empty String for the local directory in addition to null.
Add logging to detect why return null.
Add StorageTier into Tachyon
fix some typo and format
small fix for getting block size
wrong param name in comment
turned off krb so mac users using java 7 can run tests
Merge pull request #476 from dcapwell/testdfsio-mac

turned off krb so mac users using java 7 can run tests
Merge pull request #475 from CrazyJvm/StorageDir-comment

StorageDir : wrong param name in comment
Merge pull request #439 from hsaputra/add_logging_localtempfolder

Add check for empty String for the local directory in addition to null and add logging.
tweak TachyonFS logging.
Add checkstyle support for Google code style.

Add checktyle 2.8 to the maven checkstyle plugin to be able to corretly parse Google Java style rules.

First drop to fix code based on Google style.

Fix unit tests fail.
Fix rules on imports.
Remove commneted out rules.
Add checkstyle for Google Java style of constants name.
Add rule for StaticVariableName to check for static, non-final fields.
Merge pull request #473 from hsaputra/checkstyle_goog

TACHYON-182 Add checkstyle to the maven build system so we could reduce time to do style check for contributions
tweak
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 getOpType by using Enum's static function valueOf
Attempt to lower the number of resources consumed while running tests