Make RedisAccessor abstract.

Closes spring-projects#2494

Author: jxblum

src/main/java/org/springframework/data/redis/core/RedisAccessor.java

@@ -29,7 +29,7 @@
  * @author John Blum
  * @see org.springframework.beans.factory.InitializingBean
  */
-public class RedisAccessor implements InitializingBean {
+public abstract class RedisAccessor implements InitializingBean {
 
 	/** Logger available to subclasses */
 	protected final Log logger = LogFactory.getLog(getClass());