Checkstyle rules for imports and cleanup

Fixes #529

- enforced Spring Framework ordering rules
- disallowed static imports except for specific classes in test frameworks

spring-cloud-stream-test-support/src/test/java/org/springframework/cloud/stream/test/ExampleTest.java

@@ -16,8 +16,8 @@
 
 package org.springframework.cloud.stream.test;
 
-import static org.hamcrest.CoreMatchers.equalTo;
-import static org.junit.Assert.assertThat;
+import org.junit.Test;
+import org.junit.runner.RunWith;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
@@ -35,8 +35,8 @@ import org.springframework.messaging.support.GenericMessage;
 import org.springframework.test.annotation.DirtiesContext;
 import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 
-import org.junit.Test;
-import org.junit.runner.RunWith;
+import static org.hamcrest.Matchers.equalTo;
+import static org.junit.Assert.assertThat;
 
 /**
  * Integration test that validates that {@link org.springframework.cloud.stream.test.binder.TestSupportBinder} applies

spring-cloud-stream-test-support/src/test/java/org/springframework/cloud/stream/test/matcher/MessageQueueMatcherTest.java

@@ -16,9 +16,6 @@
 
 package org.springframework.cloud.stream.test.matcher;
 
-import static org.hamcrest.CoreMatchers.*;
-import static org.junit.Assert.*;
-
 import java.util.Collections;
 import java.util.concurrent.BlockingDeque;
 import java.util.concurrent.LinkedBlockingDeque;
@@ -30,6 +27,9 @@ import org.junit.Test;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.support.GenericMessage;
 
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertThat;
+
 /**
  * Tests for MessageQueueMatcher.
  *