Merge window operator commit to master

This is from commit http://github.com/RallySoftware/RxJava/commit/71335e4ed1531b1542c7b304a6d3337145e0b2df

Author: Bob Cotton

rxjava-core/src/main/java/rx/Observable.java

@@ -15,6 +15,6 @@
  */
 package rx.util;
 
-public interface BufferClosing {
+public interface Closing {
     // Tagging interface for objects which can close buffers.
 }

rxjava-core/src/main/java/rx/operators/ChunkedOperation.java

@@ -15,13 +15,13 @@
  */
 package rx.util;
 
-public class BufferClosings {
+public class Closings {
 
-    public static BufferClosing create() {
-        return new BufferClosing() {};
+    public static Closing create() {
+        return new Closing() {};
     }
 
-    private BufferClosings() {
+    private Closings() {
         // Prevent instantation.
     }
 }

rxjava-core/src/main/java/rx/operators/OperationBuffer.java

@@ -15,6 +15,6 @@
  */
 package rx.util;
 
-public interface BufferOpening {
+public interface Opening {
     // Tagging interface for objects which can open buffers.
 }

rxjava-core/src/main/java/rx/operators/OperationWindow.java

@@ -15,13 +15,13 @@
  */
 package rx.util;
 
-public class BufferOpenings {
+public class Openings {
 
-    public static BufferOpening create() {
-        return new BufferOpening() {};
+    public static Opening create() {
+        return new Opening() {};
     }
 
-    private BufferOpenings() {
+    private Openings() {
         // Prevent instantation.
     }
 }