Adding missing Logger interface.

logger.go

@@ -0,0 +1,29 @@
+/**
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package realis
+
+type Logger interface {
+	Println(v ...interface{})
+	Printf(format string, v ...interface{})
+	Print(v ...interface{})
+}
+
+type NoopLogger struct{}
+
+func (NoopLogger) Printf(format string, a ...interface{}) {}
+
+func (NoopLogger) Print(a ...interface{}) {}
+
+func (NoopLogger) Println(a ...interface{}) {}