Remove extra markdown-it-decorate

Author: rstacruz

package.json

@@ -21,7 +21,6 @@
   "devDependencies": {
     "expect": "1.12.0",
     "istanbul": "0.3.21",
-    "markdown-it-decorate": "0.3.1",
     "mocha": "2.3.3",
     "mocha-clean": "0.4.0",
     "mocha-standard": "1.0.0",