add dateForKey and allKeys methods
Make the defaultTimeoutInterval apply to all caches, not just the global one.
Merge pull request #30 from ferlatte/fix-default-timeout

Make the defaultTimeoutInterval apply to all caches
Merge pull request #28 from bm-i/master

Add dateForKey and allKeys methods
fixed a _diskQueue's priority.
Merge pull request #39 from MBKwon/master

fixed a _diskQueue's priority.
Merge with origin