Fix the bug mentioned in [TACHYON-66]

Fix the bug mentioned in [TACHYON-66] "The memory usage statistics is
not right when multi-user cache the same file and stops their
connection".
Change the synchronized range
made a few classes implement closeable
Add a unit test for cacheBlock

Add a unit test for cacheBlock
Merge pull request #370 from dcapwell/implement-closable

made a few classes implement closeable
stop can target a component
Merge remote-tracking branch 'upstream/master' into TACHYON-66
Update the UT to be concurrent

Update the UT to be concurrent and merge with the latest master branch.
Update the test code

Update the test code
Merge pull request #354 from PasaLab/TACHYON-66

[TACHYON-66] Fix the bug of the memory usage statistics in tachyon.worker.WorkerStorage
Merge pull request #375 from dcapwell/kill-component

stop can target a component
1. use google formatter; 2. basic format of all files.
temporarily remove preamble of all files.
Merge pull request #378 from zhaozhang/master

temporarily remove preamble of all files.
minor format tweak
Merge branch 'master' of github.com:amplab/tachyon
Merge branch 'amplab' into speedup