Add flexbox fixes for < IE9 to make the greedy nav button visible

Run through Autoprefixer

Update GreedyNav to use flexbox instead of `display: table`
- ref #836

Update GreedyNav.js

Replace with relative sizes

Update GreedyNav.js

Fix bug - include section for Discourse embedded comments (#825)

Merge branch 'release/4.2.1' into develop

Bump version to 4.2.1

Update CHANGELOG and history

Pagination now works for index.html files in subfolders. Links to next page consider baseurl now. (#764)

* Links to next page consider baseurl now.

* paginate_show_page_num controls whether page number gets output.

Add https prefix to google-universal embed code. (#772)

Merge branch 'release/4.2.0' into develop

Bump version to 4.2.0

Bump jekyll-sitemap to (1.0)

Update CHANGELOG and history

Add video header support to `archive` and `splash` layouts

Rename `responsive_video` helper to `video`

Add some white-space below video embeds

Add Nepali (Nepalese) text