Implement Nodemailer for test emails

This fixes a few bugs and implements email testing:

* Fix error in JSON watch path
* Update partials watch path to account for nested partials
* Implement Nodemailer and Grunt send task (thanks to @dwightjack and his [Grunt Email Boilerplate](https://github.com/dwightjack/grunt-email-boilerplate) for inspiration)
* Updated the `htmlbuild` task and tags to have the basic stylesheet also printed out in a `<style>` tag, allowing for usage of web fonts and other things that get stripped