Improve HAProxy link text; Link to API for /v2/tasks
Let GitHub Pages set utf-8 charset

GH Pages correctly sends a `Content-Type:text/html; charset=utf-8`
header, which means the document should not supply a meta charset.
Add collapsible nav from Bootstrap

* Switch to jsdeliver.net for assets so all assets come from a single
  CDN and save on multiple DNS lookups.
Correct emphasis Markdown wrapping
Link to other docs instead of the wiki