Issue #61 Added javadoc
issue #61 let the caller decide on the `TimeUnit`
Issue #61 Got rid of CacheAccessException on Store.close()
Merge pull request #68 from alexsnaps/issue-61

Approved and merged.
 #54 import latest CHMv8 code from Concurrency JSR-166 Interest Site (http://gee.cs.oswego.edu/dl/concurrency-interest/index.html)

Original CVS versions:
ConcurrentHashMap.java    : 1.257
CountedCompleter.java     : 1.47
ForkJoinPool.java         : 1.225
ForkJoinTask.java         : 1.89
ForkJoinWorkerThread.java : 1.65
ThreadLocalRandom.java    : 1.29
 #54 port CHMv8 code and add our tests
Merge branch 'issue-54'