Add auto imports for integration testing

JUnit tests can now be @SpringApplicationConfiguration
and @IntegrationTest without any explicit imports. Also
makes @RunWith(SpringJUnit4ClassRunner) optional.

Fixes gh-969

spring-boot-cli/test-samples/integration.groovy

@@ -0,0 +1,23 @@
+@SpringApplicationConfiguration(classes=Application)
+@IntegrationTest
+class BookTests {
+	@Autowired
+	Book book
+	@Test
+	void testBooks() {
+		assertEquals("Tom Clancy", book.author)
+	}
+}
+
+@Configuration
+class Application {
+	@Bean
+	Book book() {
+		new Book(author: "Tom Clancy", title: "Threat Vector")
+	}
+}
+
+class Book {
+	String author
+	String title
+}