leverage Greenwood build for generating the list of posts for blog posts page

[thescientist13]

more of a feature request for Greenwood, but essentially instead of having to maintain a list of all the blog posts

## 2018
- [Contributary 💡](/blog/2018/11/19)
- [Building A Better Mouse Trap 🧀](/blog/2018/10/28)
- etc

## 2017
- [Publishing My First Docker Image 📝](/blog/2017/10/15)
- [New OSS Project - Vue Webapp Seed 💡](/blog/2017/09/10)
etc

Have this come from the build so that the pages could be looped over programmatically instead.

This would pair really well with exposed front matter via the build so that while looping, individual pages could be sorted / processed by date, title, etc