Update Samples and Guides to use Lettuce

Favor lettuce because of multiplexing and improved scalability.
Using lettuce requires a fixed number of connections hence using
lettuce improves application scalability.

Fixes gh-652

samples/httpsession-xml/build.gradle

@@ -3,8 +3,11 @@ apply from: TOMCAT_7_GRADLE
 apply from: SAMPLE_GRADLE
 
 dependencies {
-	compile project(':spring-session-data-redis'),
-			"org.springframework:spring-web:$springVersion",
+	compile(project(':spring-session-data-redis')) {
+		exclude module: 'jedis'
+	}
+	compile "org.springframework:spring-web:$springVersion",
+			"biz.paluch.redis:lettuce:$lettuceVersion",
 			"org.webjars:bootstrap:$bootstrapVersion",
 			"org.webjars:webjars-taglib:$webjarsTaglibVersion",
 			jstlDependencies

samples/httpsession-xml/src/main/webapp/WEB-INF/spring/session.xml

@@ -13,6 +13,6 @@
 	<bean class="org.springframework.session.data.redis.config.annotation.web.http.RedisHttpSessionConfiguration"/>
 
 	<!--2-->
-	<bean class="org.springframework.data.redis.connection.jedis.JedisConnectionFactory"/>
+	<bean class="org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory"/>
 	<!-- end::beans[] -->
 </beans>