Make server match github for content-type (#505)

Unity assumes the server is configured so that when it asks
for a file that ends in .gz the content-type is set to gzip.
Servez makes that the default.

Turning off that feature makes it match github pages which
don't do this.

Author: greggman

package.json

@@ -15,7 +15,7 @@
     "build": "node build/tools/build.js",
     "start": "node build/tools/serve.js",
     "serve": "node build/tools/serve.js",
-    "server": "servez out",
+    "server": "servez --no-unity-hack out",
     "watch": "rollup -c -w",
     "export": "npm run build"
   },