change version openseadragon

package.json

@@ -22,7 +22,7 @@
     "gulp": "3.9.1",
     "semantic-ui": "2.2.4",
     "leaflet": "^1.2.0",
-    "openseadragon": "^2.3.1",
+    "openseadragon": "~2.3.1",
     "stream-series": "^0.1.1",
     "timelinejs3": "^3.4.0"
   }