Small cleanup in the testing docs.

* Remove reference to running core tests, they don't work with the test
  shell anymore.
* Replace Posts with Articles. This makes the examples more consistent
  with the rest of the docs, and removes confusion around HTTP POST and
  blog Posts.
Merge pull request #1075 from cakephp/3.0-core-testing

Small cleanup in the testing docs.
Documenting Collection::insert(), refs #1076
Fixed a few mistakes
Adding small note about what type of element insert can operate on
Merge pull request #1079 from cakephp/3.0-collection-insert

Documenting Collection::insert(), refs #1076
Capitalize CLI acronym
Exclude Improve this Doc button on search page, references #1084
Add note about Improve this Doc in contributing doc
Remove double webroot.

Fixes #1087
Cover the primary argument in beforeFind.

More specific docs about applying resultFormatters, will be done
separately.

Refs #1077
Update table-objects.rst

Correct sentence in beforeFind docs.
Merge pull request #1096 from cakephp/3.0-beforefind

Cover the primary argument in beforeFind.
Start queryFormatter docs.
Add docs on associated query builders.
Fix typos in Collection examples
Merge pull request #1105 from majna/patch-4

Fix typos in Collection examples
Merge pull request #1106 from cakephp/3.0-formatresults

3.0 formatresults
Use collection methods instead of array offsets.
Remove extra equal sign, case title