Prometheus 2.9 requires Go 1.12+ to build it from source
This commit updates the README file according to this requirement
Signed-off-by: Vandewilly Silva <vandewilly.oli.silva@hpe.com>

Signed-off-by: vanduc95 <ducnguyenvan.bk@gmail.com>

Move the `build` badge to the badge list.
Signed-off-by: zhulongcheng <zhulongcheng.me@gmail.com>

Signed-off-by: noqcks <benny@noqcks.io>

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

Signed-off-by: Glenn McDonald <2371316+glenn-m@users.noreply.github.com>

10b2e8c6 pulled new TSDB, which uses `math/bits` package introduced in Go 1.9

You start by saying that you need >= Go 1.8, then you say you need the Go 1.5 flag `GO15VENDOREXPERIMENT`, which was made default in Go 1.6.

* Test Longer Tests in Travis
Signed-off-by: Goutham Veeramachaneni <cs14btech11014@iith.ac.in>

* Make test Target Run All Tests

* Add test-short to run short tests

test is running all the tests now as we are running make tests in
CircleCI and I think the base image is shared across Prometheus Org.
Signed-off-by: Goutham Veeramachaneni <cs14btech11014@iith.ac.in>

* Remove Empty Line
Signed-off-by: Goutham Veeramachaneni <cs14btech11014@iith.ac.in>

* added docker run command to readme

* updated codebox in readme

The relative links don't work in other pages that render the README (for example https://hub.docker.com/r/prom/prometheus/). As they are (hopefully) not due to change any time soon, I think using absolute links is better.

A simple reference to the CNCF and link to the website.

building tool

For building from source as an end user running the tests is not necessary.

It's almost at an end, so we can remove this.

Fixes https://github.com/prometheus/prometheus/issues/1165

As DigitalOcean is linking to this page, direct users to the project list from here.