Update should-equal to fix bug with calling .toString while using ==

Author: btd

package.json

@@ -39,7 +39,7 @@
   "main": "./index.js",
   "license": "MIT",
   "dependencies": {
-    "should-equal": "0.7.2",
+    "should-equal": "0.7.3",
     "should-format": "0.3.2",
     "should-type": "0.2.0"
   }