add block handler to handle block files on different under file systems
add BlockHandlerHdfs as stub
Trying to fix HBase support issue in TACHYON-27
change isHadoopUnderFS() in UnderFileSystem to be public, and use it in BlockHandler
modify comment format and gramma mistakes
some format fix
Optimize imports; reformat code style; improve javadoc; remove the commented code.
Linked to TACHYON-46 in Javadoc
Improve Javadoc comments
Merge branch 'master' of https://github.com/amplab/tachyon into createNonRecursive
createNonRecursive() should throw exception if parent directory doesn't already exist,  which is extremely important for HBase to do fencing of dead region servers properly.
modify retrieveByteBufferFromRemoteMachine in TachyonFile.java according to new interface just like RemoteBlockInStream.java
add test case for TachyonFile
close the buffer after Assert
[TACHYON-65] Fix the listFiles method

[TACHYON-65] the ListFiles(path,recursive) function of
tachyon.master.MasterInfo class does not work well
log stack traces on error and keep error history
modify according to the comments, format change
fix typo
change error message
Merge pull request #352 from dcapwell/client-stacktrace

log stack traces on error and keep error history