Always use UTF-8 when copying resources

This way the build isn't platform dependent.

Change-Id: Ib8d4a48ede1c711e8c1b56e45c50428df436988f
Signed-off-by: Shawn O. Pearce <sop@google.com>
diff --git a/pom.xml b/pom.xml
index 70ad8c9..c8025bc 100644
--- a/pom.xml
+++ b/pom.xml
@@ -254,6 +254,12 @@
 
   <properties>
     <gwtVersion>1.6.4</gwtVersion>
+    <project.build.sourceEncoding>
+      UTF-8
+    </project.build.sourceEncoding>
+    <project.reporting.outputEncoding>
+      UTF-8
+    </project.reporting.outputEncoding>
   </properties>
 
   <build>