Support custom classloader for Redis deserialization

[cb372]

Support passing a custom classloader to RedisCache for use in deserialization. This is needed in order to deserialize correctly when integrating with Play Framework.

Fixes #32

[coveralls]

Coverage increased (+0.08%) to 95.02% when pulling 42f432e on issue32 into 912fb8a on master.

[coveralls]

Coverage increased (+0.22%) to 95.17% when pulling 47ea30c on issue32 into 912fb8a on master.

[coveralls]

Coverage increased (+0.07%) to 95.17% when pulling 245a2ce on issue32 into dd086c7 on master.

[coveralls]

Coverage increased (+0.07%) to 95.17% when pulling 34bf2e6 on issue32 into dd086c7 on master.