use master hostname in conf/tachyon-env.sh as default.
show disk usage
user NoWorkerException instead of NoLocalWorkerException
fix null pointer bug in blockinstream
add replication and blocksize parameter to underfs interface.
temp fix for replication factor for hdfs
fix of bin/start.sh hangs by redirecting output to the null device.
Merge pull request #36 from hobinyoon/master

fix of bin/start.sh hangs by redirecting output to the null device.