Use incremental builds rather than full builds

In this project, we can use the following command to test examples.
  `$ npm test`

It might be very inefficient, especially, if the number of files
increases. So, it's better to use incremental builds rather than full
builds. We can accomplish this by combining `configure` and `build`
commands instead of `rebuild` command.

package.json

@@ -30,7 +30,7 @@
     "url": "git://github.com/nodejs/node-addon-api.git"
   },
   "scripts": {
-    "pretest": "node-gyp rebuild -C test",
+    "pretest": "node-gyp configure build -C test",
     "test": "node test",
     "doc": "doxygen doc/Doxyfile"
   },