Issue #147 - Add non-bulk Ehcache unit tests

Adds unit tests for the following Ehcache methods:

* get
* put
* containsKey
* remove(key)
* clear
* iterator
* putIfAbsent
* remove(key, value)
* replace(key, value)
* replace(key, oldValue, newValue)
Is there anything we want to assert about the state of the Store in this case? I'm guessing it is still not empty, but maybe that isn't something we can/should assert. not sure