Fix bug with stale state in http request factory

If we don't re-use an existing factory, the label doesn't change and
all the snippets get generated with the same identifier.

Remove explicit version from wiremock test

Add snippets attribute to build config

See gh-295

initializr-web/src/test/groovy/io/spring/initializr/web/test/MockMvcClientHttpRequestFactoryTestExecutionListener.java

@@ -39,6 +39,8 @@ public final class MockMvcClientHttpRequestFactoryTestExecutionListener
 					beanFactory.getBean(MockMvc.class));
 			beanFactory.registerSingleton("mockMvcClientHttpRequestFactory",
 					this.factory);
+		} else {
+			factory = beanFactory.getBean("mockMvcClientHttpRequestFactory", MockMvcClientHttpRequestFactory.class);
 		}
 	}