* Fast path the merge querier such that it is completely removed from query path when there is no remote storage.

* Add NoopQuerier

* Add copyright notice.

* Avoid global, use a function.

Revert "Bypass the fanout storage merging if no remote storage is configured."

Update remote storage APIs from 1.8 branch

This reverts commit 0997191b.

Removes configurability introduced in #3160 in favour of hard-coding,
per advice from @brian-brazil.

Bypass the fanout storage merging if no remote storage is configured.

Tsdb StartTime : Use a simplier way to compute StartTime

storage/tsdb: check that max block duration is larger than min

Remove .codeclimate.yml

See https://github.com/prometheus/prometheus/pull/3333#issuecomment-339209982

If the user accidentally sets the max block duration smaller than the min,
the current error is not informative.  This change just performs the check
earlier and improves the error message.

Cut v2.0.0-rc.2

* Allow getting credentials via EC2 role

This is subtly different than the existing `role_arn` solution, which
allows Prometheus to assume an IAM role given some set of credentials
already in-scope. With EC2 roles, one specifies the role at instance
launch time (via an instance profile.) The instance then exposes
temporary credentials via its metadata. The AWS Go SDK exposes a
credential provider that polls the [instance metadata endpoint][1]
already, so we can simply use that and it will take care of renewing the
credentials when they expire.

Without this, if this is being used inside EC2, it is difficult to
cleanly allow the use of STS credentials. One has to set up a proxy role
that can assume the role you really want, and launch the EC2 instance
with the proxy role. This isn't very clean, and also doesn't seem to be
[supported very well][2].

[1]:
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-metadata.html
[2]: https://github.com/aws/aws-cli/issues/1390

* Automatically try to detect EC2 role credentials

The `Available()` function exposed on ec2metadata returns a simple
true/false if the ec2 metadata is available. This is the best way to
know if we're actually running in EC2 (which is the only valid use-case
for this credential provider.)

This allows this to "just work" if you are using EC2 instance roles.

In some places, where ctxhttp or gRPC are concerned, we still need to use the
old contexts.

I left the promql ones and some others untouched as I remember that @fabxc
prefers them that way.

staticcheck fails with:
storage/remote/read_test.go:199:27: do not pass a nil Context, even if a function permits it; pass context.TODO if you are unsure about which Context to use (SA1012)

Kingpin now automatically does this via --version.

Hey, branding :)