Set specific file-saver version

Newer version changed how it exports the package, and when that's
fixed the function doesn't actually save the file. Should be okay
to update to 1.3.6 and beyond once that's available on npm.

eligrey/FileSaver.js#415

package.json

@@ -88,7 +88,7 @@
     "express-useragent": "^1.0.4",
     "extract-text-webpack-plugin": "^3.0.1",
     "fastclick": "~1.0.3",
-    "file-saver": "^1.3.3",
+    "file-saver": "1.3.3",
     "geoip-lite": "^1.1.6",
     "graceful-fs": "~2.0.1",
     "gridfs-stream": "~1.1.1",