rake stats for engines
Merge pull request #15299 from andriytyurnikov/engine_friendly_rake_stats

rake stats for engines
Improve readability of Explain Queries table in guides [ci skip]
Merge pull request #15303 from JohnKellyFerguson/guides-ar-querying

Improve readability of Explain Queries table in guides
integration tests do not need to load fixtures by hand

I don't know when this changed, checked back up to 3.2 and integration
tests instantiate fixtures just fine.
Update all Rails 4.1.0 references in guides to 4.1.1 [ci skip]
Merge pull request #15304 from JohnKellyFerguson/guides-4.1.1

Update all Rails 4.1.0 references in guides to 4.1.1 [ci skip]
unwrap the constraints object on initialization, eliminate loops

Unwrap Constraints objects.  I don't actually think it's possible
to pass a Constraints object to this constructor, but there were
multiple places that kept testing children of this object.  I
*think* they were just being defensive, but I have no idea.
Remove unnecessary require of Minitest.

Minitest has already been required when calling Minitest.autorun.
Merge pull request #15305 from tgxworld/remove_unnecessary_require

Remove unnecessary require of Minitest.
The correct status to test should be :switching_protocols.
Convert source to string if it is present.
Merge pull request #15311 from zuhao/refactor_actionpack_bare_metal_test

The correct status to test should be :switching_protocols.
Merge pull request #15312 from JuanitoFatas/action_view/asset_path

Convert source to string if it is present.
[ci skip] Update GFM link in guides guidelines.

Also remove a duplicated sentence.
Merge pull request #15315 from JuanitoFatas/guides-guidelines

[ci skip] Update GFM link in guides guidelines.