Use static factory methods and proxyBeanMethods = false

It is better to be explicit about beans of type `Module` and make
sure they don't interfere with Spring trying to enhance
`@Configuration` classes. The tests are now clear of the pesky
warning logs, and there is a new section in the README.

src/test/java/org/springframework/guice/ScopingTests.java

@@ -91,7 +91,7 @@ public class ScopingTests {
 	static class ScopingTestsConfig {
 
 		@Bean
-		Module module() {
+		static Module module() {
 			return new AbstractModule() {
 				@Override
 				protected void configure() {