minor #3807 Added some exceptions to the method order in CS (stof)

This PR was merged into the 2.3 branch.

Discussion
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Added some exceptions to the method order in CS

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | n/a

See silexphp/Silex#936 (comment) for the reason. Formalizing this case in the doc is a good idea IMO.

Commits
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3b8e644 Added some exceptions to the method order in CS

contributing/code/standards.rst

@@ -101,7 +101,10 @@ Structure
 
 * Declare class properties before methods;
 
-* Declare public methods first, then protected ones and finally private ones;
+* Declare public methods first, then protected ones and finally private ones. 
+  The exceptions to this rule are the class constructor and the ``setUp`` and 
+  ``tearDown`` methods of PHPUnit tests, which should always be the first methods
+  to increase readability.
 
 * Use parentheses when instantiating classes regardless of the number of
   arguments the constructor has;