issue #72 - cache expiration
Merge pull request #140 from timeck/issue-72

issue #72 - cache expiration
extra key/value type checks in compute() and bulkCompute() methods
Merge pull request #141 from timeck/someExtraChecks

extra key/value type checks in compute() and bulkCompute() methods
Issue #41: Initial cut of cache event listener notification layer and relevant plumbing, though no actual events are wired in yet.