Extract and make CompressFlags public

Fixes https://github.com/openstreetmap/OSM-binary/issues/68

src.java/crosby/binary/file/BlockOutputStream.java

@@ -25,10 +25,6 @@ import java.io.OutputStream;
 import java.util.ArrayList;
 import java.util.List;
 
-enum CompressFlags {
-    NONE, DEFLATE
-}
-
 public class BlockOutputStream implements Closeable, Flushable {
 
     public BlockOutputStream(OutputStream output) {

src.java/crosby/binary/file/CompressFlags.java

@@ -0,0 +1,5 @@
+package crosby.binary.file;
+
+public enum CompressFlags {
+    NONE, DEFLATE
+}