Add infrastructure for "Updates" page

@tilomitra here's the basic setup for the Updates page. Here are some things I was thinking while building it:

- [x] Add version and data info for each "post", possibly styled next to each heading.
- [x] Create `updates.css` file.
- [x] Make sure links to HISTORY.md are called out.
- [ ] Add proper URLs once 0.2.0 has been released.

I think the theme for the first update is essentially around applying the first round of feedback we got from people (yay! Contributors), and how we fixed some basic bugs and greatly improved developer workflow for contributors.