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/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