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/websocket/build.gradle

@@ -16,8 +16,10 @@ apply from: SAMPLE_GRADLE
 group = 'samples'
 
 dependencies {
-	compile project(':spring-session-data-redis'),
-			"org.springframework.boot:spring-boot-starter-web",
+	compile(project(':spring-session-data-redis')) {
+		exclude module: 'jedis'
+	}
+	compile "org.springframework.boot:spring-boot-starter-web",
 			"org.springframework.boot:spring-boot-starter-data-jpa",
 			"org.springframework.boot:spring-boot-starter-thymeleaf",
 			"org.springframework.boot:spring-boot-starter-websocket",
@@ -25,6 +27,7 @@ dependencies {
 			"org.springframework.data:spring-data-jpa",
 			"nz.net.ultraq.thymeleaf:thymeleaf-layout-dialect",
 			"org.thymeleaf.extras:thymeleaf-extras-conditionalcomments",
+			"biz.paluch.redis:lettuce:$lettuceVersion",
 			"org.webjars:bootstrap:$bootstrapVersion",
 			"org.webjars:html5shiv:$html5ShivVersion",
 			"org.webjars:knockout:2.3.0",