It's not explicitly clear that a higher priority number means the method is called earlier. Add some verbiage to that effect.

…at we have 2.0, 2.1, 2.2 and master

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | symfony#2290

[symfony#2273] Add valid values for currency

Fix two minor typos in the contributing section

…cher

Add a clarification to the event subscriber section

…-bump

[2.0] Re-working contributing language for 2.2 branch

[Book] Fixed highlighting issues

add some minor interpunction fixes for consistency

…rJ-patch-13

Conflicts:
	contributing/documentation/overview.rst

…rm_option

[Typo] Fixing typo in date_format form option description

Do not work anymore.

[symfony#2290] Single command apps with arguments

…and explains how to override the getDefinition method