Add blog post about service discovery

Indicate WITH keyword as optional in alerting docs.

Fix run-on sentence, improve increase() doc wording.

Add initial documentation for the alertmanager.

Add a new section for alerting so it's all together,
and move the alerting rules over there.

Document increase() function.

Improve wording in the naming section even more.

This should have been part of
https://github.com/prometheus/docs/pull/95, but somehow I missed to
commit it.

document caveat about combining sum and rate

As per https://groups.google.com/d/msg/prometheus-developers/wfGhGkDcZ3Q/SXv4aDGgKY8J

Sanitize and uniquify in-page anchors properly.

Improve Configuration / SD documentation.

Things like question marks or parentheses don't play nicely in URLs in
many contexts. Replace all special characters with dashes, and also
ensure that anchors are unique within a page if there are headers with
identical texts.

Document changes() and resets() functions.

Add memcached-exporter to list of exporters.

Two minor docs improvements.

This is relevant for users building directly from the GitHub repo.

Fixes https://github.com/prometheus/docs/issues/91 .

Fixes https://github.com/prometheus/docs/issues/82 .

Remove duplicated reloading docs

Change configuration example URL

Add basic auth and reloading to configuration docs

Add config docs for file discovery

Add consul SD documentation