Converts index.html to templates/index.jade

* post meta abstracted to jade partial to share between index and post
* wintersmith-tags plugin added and implemented
* default layout made to accommodate index as well as posts
Converts pagination on index.jade

* Patches paginator plugin to return currentPage and totalPages properties
Configs extend config.json

* Installs grunt-extend
* Global properties moved into config.json, environment-specific properties moved out