Speed up npm dependency checking when running 'make dev'

When package.json changes, use 'check-dependencies' to do
a lightweight offline-only check of whether the installed
packages match the versions specified in package.json
before running the much slower 'npm install' to actually
install any missing dependencies.

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",