Add cachebusting fingerprints to asset files.

This is using http://avdgaag.github.io/nanoc-cachebuster/.

docs.css had to be moved out of /static because the static datasource
treats all files as binary, and thus no textual filters can be applied
(necessary for rewriting the jumbotron background image URL).

Fixes https://github.com/prometheus/docs/issues/369

List unofficial Common Lisp client

https://github.com/deadtrickster/prometheus.cl

add notice for default behavior of using 3GB RAM

Clarify replace relabel behavior with non-matching regex

Fix blog sidenav.

This got broken in https://github.com/prometheus/docs/pull/365

Improve search engine result presentation

- best to keep title length under 55 characters
- descrioption should not be longer than 150-160 characters

Link to community section

Collapse inactive navigation menus

Use javascript to hide all inactive menu items and only show one active
menu item at a time.

Set descriptive front page title

The title of the homepage is used in Google search results.

document pushover configuration

fixes #345

Update link to Michael Stapelberg's German introduction talk

He gave a more up-to-date version of his previous talk at Easterhegg
2016. I think it makes more sense to link the newer talk here instead
of the old one.

Add docs for Nerve SD.

Fixes #298

Add GitHub star button to header.

Add a link to nginx-lua-prometheus

Add life360 logo to blog post

Add user interview with Life360

Mention CPU cores in peak performance benchmark.

Add PromCon link to landing page jumbotron.