Provide a default output directory for snippets based on build tool

Rather than requiring an output directory to be explcitly configured,
a default is now automatically configured based on the build tool
that's being used. When using Gradle, snippets will be generated in
build/generated-snippets. When using Maven, snippets will be
generated in target/generated-snippets.

See gh-297

samples/rest-assured/src/test/java/com/example/restassured/SampleRestAssuredApplicationTests.java

@@ -42,7 +42,7 @@ import com.jayway.restassured.specification.RequestSpecification;
 public class SampleRestAssuredApplicationTests {
 
 	@Rule
-	public final JUnitRestDocumentation restDocumentation = new JUnitRestDocumentation("build/generated-snippets");
+	public final JUnitRestDocumentation restDocumentation = new JUnitRestDocumentation();
 	
 	private RequestSpecification documentationSpec;
 	

samples/rest-notes-slate/src/test/java/com/example/notes/ApiDocumentation.java

@@ -61,7 +61,7 @@ import com.fasterxml.jackson.databind.ObjectMapper;
 public class ApiDocumentation {
 
 	@Rule
-	public final JUnitRestDocumentation restDocumentation = new JUnitRestDocumentation("build/generated-snippets");
+	public final JUnitRestDocumentation restDocumentation = new JUnitRestDocumentation();
 
 	@Autowired
 	private NoteRepository noteRepository;

samples/rest-notes-spring-data-rest/src/test/java/com/example/notes/ApiDocumentation.java

@@ -61,7 +61,7 @@ import com.fasterxml.jackson.databind.ObjectMapper;
 public class ApiDocumentation {
 	
 	@Rule
-	public final JUnitRestDocumentation restDocumentation = new JUnitRestDocumentation("target/generated-snippets");
+	public final JUnitRestDocumentation restDocumentation = new JUnitRestDocumentation();
 
 	@Autowired
 	private NoteRepository noteRepository;

samples/rest-notes-spring-data-rest/src/test/java/com/example/notes/GettingStartedDocumentation.java

@@ -58,7 +58,7 @@ import com.jayway.jsonpath.JsonPath;
 public class GettingStartedDocumentation {
 	
 	@Rule
-	public final JUnitRestDocumentation restDocumentation = new JUnitRestDocumentation("target/generated-snippets");
+	public final JUnitRestDocumentation restDocumentation = new JUnitRestDocumentation();
 
 	@Autowired
 	private ObjectMapper objectMapper;

samples/rest-notes-spring-hateoas/src/test/java/com/example/notes/ApiDocumentation.java

@@ -70,7 +70,7 @@ import com.fasterxml.jackson.databind.ObjectMapper;
 public class ApiDocumentation {
 	
 	@Rule
-	public final JUnitRestDocumentation restDocumentation = new JUnitRestDocumentation("build/generated-snippets");
+	public final JUnitRestDocumentation restDocumentation = new JUnitRestDocumentation();
 	
 	private RestDocumentationResultHandler documentationHandler; 
 

samples/rest-notes-spring-hateoas/src/test/java/com/example/notes/GettingStartedDocumentation.java

@@ -61,7 +61,7 @@ import com.jayway.jsonpath.JsonPath;
 public class GettingStartedDocumentation {
 	
 	@Rule
-	public final JUnitRestDocumentation restDocumentation = new JUnitRestDocumentation("build/generated-snippets");
+	public final JUnitRestDocumentation restDocumentation = new JUnitRestDocumentation();
 
 	@Autowired
 	private ObjectMapper objectMapper;

samples/testng/src/test/java/com/example/testng/SampleTestNgApplicationTests.java

@@ -39,7 +39,7 @@ import org.testng.annotations.Test;
 @WebAppConfiguration
 public class SampleTestNgApplicationTests extends AbstractTestNGSpringContextTests {
 
-	private final ManualRestDocumentation restDocumentation = new ManualRestDocumentation("build/generated-snippets");
+	private final ManualRestDocumentation restDocumentation = new ManualRestDocumentation();
 
 	@Autowired
 	private WebApplicationContext context;