Update for Prometheus 2.3

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>

* Just one char typo

Also added simple example to usage documentation.
Signed-off-by: Ľubomír Varga <lubomir.varga@nike.sk>

Signed-off-by: Rohit Agarwal <mindprince@gmail.com>

Signed-off-by: Richard Hartmann <richih@richih.org>

Signed-off-by: pvdvreede <pvdvreede@gmail.com>

That URL is not the best, but it's better than nothing
Signed-off-by: Richard Hartmann <richih@richih.org>

Add saved_replies.md

Closes https://github.com/prometheus/prometheus/issues/4196

Signed-off-by: Richard Hartmann <richih@richih.org>

Signed-off-by: Richard Hartmann <richih@richih.org>

Signed-off-by: Richard Hartmann <richih@richih.org>

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>

Signed-off-by: Nemo <me@captnemo.in>

Signed-off-by: Marcin Budny <marcin.budny@gmail.com>

Signed-off-by: James Turnbull <james@lovedthanlost.net>

Remove broken link to logo author's website

The website doesn't exist anymore and no comparable online presence
exists.

Fixes https://github.com/prometheus/docs/issues/794Signed-off-by: Julius Volz <julius.volz@gmail.com>

Signed-off-by: Juan Paulo Gutierrez <juanpaulo.gutierrez@gmail.com>

* Improve the wording of the defintion of a Counter

* Link to the wikipedia article on Montonic functions.
* Mention that counters can be reset to zero.
* Change language to speak directly to the user.
Signed-off-by: Ben Kochie <superq@gmail.com>

* Fixup "that can decrease"
Signed-off-by: Ben Kochie <superq@gmail.com>

* Point out that docs are open source and can be edited
Signed-off-by: Julius Volz <julius.volz@gmail.com>

* Add contribution clarifications to README.md, link to it
Signed-off-by: Julius Volz <julius.volz@gmail.com>

Signed-off-by: bhois <bernd.hois@bearingpoint.com>

Signed-off-by: Berant Lemmenes <berant@lemmenes.com>

code.shutterstock.com doesn't exist anymore, apparently.
Signed-off-by: Michael Weibel <mweibel@users.noreply.github.com>

Signed-off-by: Zachary Romero <zacromero3@gmail.com>

* alerting: update Slack configuration
* alerting: re-order Slack parameters
Signed-off-by: Simon Pasquier <spasquie@redhat.com>

Signed-off-by: Marcin Budny <marcin.budny@gmail.com>

Add Minio to list of software exposing Prometheus metrics
Signed-off-by: Nitish Tiwari <nitish@minio.io>

Signed-off-by: Timon Wong <timon86.wang@gmail.com>

* FreshTracks provides a hosted prometheus service with goals to help
enhance existing monitoring solutions
* check us out at https://freshtracks.ioSigned-off-by: John T Skarbek <jtslear@gmail.com>

Signed-off-by: Ben Kochie <superq@gmail.com>

Signed-off-by: beorn7 <beorn@soundcloud.com>

* Add Wechat configuration
Signed-off-by: Simon Pasquier <spasquie@redhat.com>

* Add more Wechat configuration options
Signed-off-by: Simon Pasquier <spasquie@redhat.com>

* Address review comments
Signed-off-by: Simon Pasquier <spasquie@redhat.com>

fix indentation on node_exporter example

Signed-off-by: Ben Bleything <ben@bleything.net>

Signed-off-by: Ivan Babrou <ibobrik@gmail.com>

Signed-off-by: Simon Pasquier <spasquie@redhat.com>