Add repository field

Just to avoid the annoying warning.

```
npm WARN package.json css-whitespace@1.1.0 No repository field.
```

Author: MoOx

package.json

@@ -14,5 +14,9 @@
   "main": "index",
   "scripts": {
     "test": "mocha --require should --reporter spec"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/reworkcss/css-whitespace.git"
   }
 }