#117 fix SPI tests by adding missing key/value type checks
 #117 move SPI test methods so we're DRY-ready once other Store implementations are on the way
 #117 fix wrongValueTypeThrowsException to make it check the value type and not the key type
Merge pull request #123 from lorban/issue-117

 #117 fix SPI tests by adding missing key/value type checks
Issue #75: wired CacheLoader where applicable.