[alerting] Add alerting support to external probe (cloudprober#532)

* Improve server mode a bit. Start reading replies before request sending is finished. This will help if you're running the probe against a bunch of targets.
* Also, while here, improve the readability of this code.

[docs] Share Cloudprober's journey through an About page. (cloudprobe…

…r#439)

* Add blog-meta shortcode to add blog-like metadata for such pages.

[oauth2] Fix a bug in HTTP token refresh. (cloudprober#422)

* While fixing the HTTP request body handling in [probes.http] Fix HTTP request body handling. cloudprober#408, I introduced a bug: that PR changed request body to be buffered all the time to simplify it. I missed changing oauth2.http_token at that time. This PR fixes that.
* Improve tests.

[probes.external] Improve the startCmdIfNotRunning test further. (clo…

…udprober#398)

* Verify that we restart the command when it stops (pause=0).

Older website design.

Update getting-started.md

Update docker image path to Github container registry.

[probes.http] Don't overwrite server_name if set in tls_config (cloud…

…prober#294) (cloudprober#295)

[probe.http] Add an option to limit redirects (cloudprober#289)

Co-authored-by: Rob Pickerill <[email protected]>

[surfacers.stackdriver] Use random task ID for Google Cloud Run. (clo…

…udprober#267)

See cloudprober#257 for the background.

Cloud Run starts/restarts the container multiple with the same revision id. This creates a problem for the Stackdriver metrics (at least in the short term) as for the cumulative metrics, a point's startTime is tied to the Cloudprober start time and its endTime cannot be before the startTime. This condition is violated if there are multiple processes exporting data to the same resource.

[surfacer.stackdriver] Ignore if we are not able to get the instance …

…info. (cloudprober#228)