Update to GWT 1.7.0

Change-Id: If53d51ea24b85c93a6702d828a47ee90d6e77658
Signed-off-by: Shawn O. Pearce <sop@google.com>
diff --git a/pom.xml b/pom.xml
index 197ac60..7afd09c 100644
--- a/pom.xml
+++ b/pom.xml
@@ -253,7 +253,7 @@
   </licenses>
 
   <properties>
-    <gwtVersion>1.6.4</gwtVersion>
+    <gwtVersion>1.7.0</gwtVersion>
     <project.build.sourceEncoding>
       UTF-8
     </project.build.sourceEncoding>