According commit [206bcfcd](https://github.com/prometheus/prometheus/commit/206bcfcdaac356e8bdb0cd91f3478f111eaa6d30)
kubeletPort config option was removed (release 0.20.0)

docs/alerting: update configuration docs

Merge next release doc into master

configuration: Update scrape config

Add missing underscore to webhook_config variable

fixed a typo

added alertmanager start example

with example config.file argument

Update kubernetes SD documentation

Update configuration documentation to present correct information about port/container selection algorithms; and to provide a warning about the requirement to expose at least one port on pods

Fix `post` values in result

Update docs for server_name in <tls_config>

Improve k8 discovery docs.

Fix formatting.
Remove long example from reference documentation, point off
to existing example instead.

Remove digitalocean/rsyslog_exporter from lost of exporters.

Closes #440

Add best pratice around operation counters

Add link to zookeeper_exporter

Replace the deprecated third-party memcached_exporter by the official one

Add yet another RabbitMQ Exporter

Remove leftover from old  behavior

Next release

Update docs for k8s pods sd

Add docs for ignoring and new group_* semantics.

re-order exporters list