add Handlebars as an npm dependency (for now)

Author: geoffp

package.json

@@ -13,6 +13,7 @@
     "grunt-contrib-copy": "^0.8.2",
     "grunt-contrib-nodeunit": "^0.4.1",
     "grunt-contrib-watch": "^0.6.1",
+    "handlebars": "^4.0.5",
     "html-entities": "^1.2.0",
     "matchdep": "^1.0.0",
     "mustache": "^2.2.0"