Fixed some blog and documentation typos.

Add Incopro interview

Added ProxySQL exporter to the list.

Add information on using pre-built / contributed dashboards.

Fix `label_replace` documentation

Updated (typos and copy clarity etc.) following PR comments.

With the fix in place, the documentation is in line with the intention
expressed by tests,
e.g. https://github.com/prometheus/prometheus/blob/master/promql/testdata/functions.test#L173-L176
and
https://github.com/prometheus/prometheus/blob/master/promql/testdata/functions.test#L195-L199
.

querying examples: fix proctype vs proc metric key

Add Compose interview

Add Cloud Foundry Firehose Exporter to documentation

Add Prometheus-Talk @ MRMCD 2016

Change vector.im -> riot.im on Community page

Vector is Riot now, see:

https://techcrunch.com/2016/09/19/riot-wants-to-be-like-slack-but-with-the-flexibility-of-an-underlying-open-source-platform/

Added GitHub Exporter to documentation

Remove examples of time metrics not using seconds

Bring visualization template example up-to-date

Add interview with Digital Ocean

Added Docker Hub exporter to list of third-party exporters

Fix small grammatical issues w/ AlertManager docs

Add Shuttlecloud user interview

Clarify the Apdex calculation.

The Apdex calculation in the histogram documentation does not actually
match the Apdex as it should be calculated, as any error states should
not be classified as satisfactory of tolerable. This can't be achieved
without including the status code in the http latency labels, which it
is not.

Added missing Exporters to exporter-list

Add standard exports into the documentation

Adds exporters that are still missing in the official documentation up to now. Fixes this.