Update .gitignore for valo

Change-Id: Ia37e982e69c5a26f8ed221a5e2ef4c7ed7bd68df

.gitignore

@@ -40,6 +40,9 @@
 /WebContent/VAADIN/themes/runo/common/img/ajax-loader-red.gif
 /WebContent/VAADIN/themes/runo/common/img/ajax-loader-yellow.gif
 
+# /WebContent/VAADIN/themes/valo/
+/WebContent/VAADIN/themes/valo/styles.css
+
 # /WebContent/VAADIN/widgetsets/
 /WebContent/VAADIN/widgetsets
 /WebContent/VAADIN/gwt-unitCache*