Proposed patch for #2589 to guard against content spoofing.
Cleanup messageFormatter example to use logs from build steps instead of directly using build logs
Remove assert from subscribeConsumer

This method is used by the WebStatus, and thus necessary (even for
new-style steps) in eight.
Catch a specific exception
Update release notes for #2589
Fix one more missing exception
Merge pull request #1246 from anish/eight-msgfmt

Cleanup messageFormatter example to use logs from build steps instead of directly using build logs
Merge pull request #1249 from djmitche/subscribeConsumer-assert

Remove assert from subscribeConsumer
Merge pull request #1244 from wmswms/eight

Guard against content spoofing.

Fixes ticket:2589
one-line-per-sentence policy for the section to update

* to make it easier to see the differences
clarify a bit the difference between master- and slave-side source steps

* emphasise the difference between them
* since master-side steps are recommended move them up in the examples
* slave-steps are deprecated and will be removed in 0.9
* emphasise that the next section is about master-side steps
apply one-sentence-per-line rule to the changed section
factor out integration-style step testing support
add an integration test that renders a new-style step
Tickle #2934
Fix checkLogfiles to not fail with new style steps
update documentation for GitHub change hook

* misc syntax, wording and cosmetic changes
* move mention of standalone server to the beginning of the section
* fix link to the GitHub tutorial for adding webhooks
* make list of parameters of GitHub webhook and their correpsonding
  values explicit

Fixes ticket:2938
Merge sa2ajj/buildbot:bugfix-2938 (PR #1253)
Fix cross-site scripting in status_json by specifying nosniff and app/json content
Merge pull request #1254 from djmitche/bug2934

Test for and fix new-style step assertions triggered by Buildbot code

Fixes ticket:2934