Merge pull request #3013 from hypothesis/speedup-npm-deps-checking

Speed up npm dependency checking when running 'make dev'

package.json

@@ -66,6 +66,7 @@
   },
   "devDependencies": {
     "chai": "^3.2.0",
+    "check-dependencies": "^0.12.0",
     "jscs": "^1.13.1",
     "karma": "^0.13.10",
     "karma-browserify": "^3.0.3",