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
simplify getOpType by using Enum's static function valueOf
Attempt to lower the number of resources consumed while running tests
recompute uses thread pool now
update documents to have a underfs page
made kill command be more polite
refactor according to comments
remove getOpType
Merge pull request #479 from dcapwell/nicekill

made kill command be more polite
Merge pull request #478 from shimingfei/simplifyGetOpType

simplify getOpType by using Enum's static function valueOf
Add suppress rule for Tachyon *Conf classes to exempt the public final members as all upper cases.
proper cleanup of resources in recompute command
Merge pull request #484 from dcapwell/closeresourcesinrecompute

proper cleanup of resources in recompute command
Merge pull request #481 from hsaputra/addexception_checkstyle_conf

Add suppress rule for Tachyon *Conf classes