fix missing imports from last commit.

Change-Id: I2114bd7894a7d07ab2a42d20add90d5fb3e9d075
Signed-off-by: Carsten Hiesserich <carsten.hie@gmail.com>
diff --git a/org.eclipse.vex.ui/src/org/eclipse/vex/ui/internal/editor/VexEditor.java b/org.eclipse.vex.ui/src/org/eclipse/vex/ui/internal/editor/VexEditor.java
index 050707d..1888a2b 100644
--- a/org.eclipse.vex.ui/src/org/eclipse/vex/ui/internal/editor/VexEditor.java
+++ b/org.eclipse.vex.ui/src/org/eclipse/vex/ui/internal/editor/VexEditor.java
@@ -18,6 +18,8 @@
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
+import java.io.PrintWriter;
+import java.io.StringWriter;
 import java.net.URI;
 import java.text.MessageFormat;
 import java.util.ArrayList;