Switch to SPDX license identifier

Hat Tip @Seldaek

Author: djallits

composer.json

@@ -2,8 +2,8 @@
     "name": "zurb/foundation"
   , "description": "The most advanced responsive front-end framework in the world."
   , "keywords": ["foundation", "scss"]
-  , "homepage": "http://foundation.zurb.com/"
+  , "homepage": "http://foundation.zurb.com"
   , "author": "ZURB Inc."
-  , "license": "MIT License"
+  , "license": "MIT"
 
 }