add should dev dependency

package.json

@@ -7,12 +7,15 @@
 , "bugs": "http://github.com/aheckmann/gm/issues"
 , "licenses": [{ "type": "MIT", "url": "http://www.opensource.org/licenses/mit-license.php"}]
 , "main": "./index"
-, "contributors":
-  [ { "name": "Aaron Heckmann", "email": "aaron.heckmann+github@gmail.com" }
-  , { "name": "Tero Parviainen", "github": "http://github.com/teropa" }
+, "contributors": [
+      { "name": "Aaron Heckmann", "email": "aaron.heckmann+github@gmail.com" }
+    , { "name": "Tero Parviainen", "github": "http://github.com/teropa" }
   ]
-, "repository":
-  { "type": "git"
-  , "url": "http://github.com/aheckmann/gm.git"
+, "repository": {
+      "type": "git"
+    , "url": "http://github.com/aheckmann/gm.git"
+  }
+, "devDependencies": {
+      "should": "0.2.1"
   }
 }