add link to form testing chapter in test section
Moved 'contributing' images to their own directory
fix name of the Yaml component

The component name that is used in the code as well as in the issue
tracker used by the symfony/symfony repository is Yaml (instead of
YAML). Therefore, this should also be the name being used in the
documentation.
replace "Symfony2" with "Symfony"
Added a note about the lacking features of Yaml Component
Fixed code highlighting
minor #4190 add link to form testing chapter in test section (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
----------

add link to form testing chapter in test section

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

The confusion in symfony/symfony#11774 made me think that we could improve the links between the testing and the form section when it comes to testing forms.

Commits
-------

a2dbd36 add link to form testing chapter in test section
minor #4199 fix name of the Yaml component (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
----------

fix name of the Yaml component

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | related to #4189

The component name that is used in the code as well as in the issue tracker used by the symfony/symfony repository is Yaml (instead of YAML). Therefore, this should also be the name being used in the documentation.

Commits
-------

5187768 fix name of the Yaml component
minor #4200 Moved 'contributing' images to their own directory (javiereguiluz)

This PR was merged into the 2.3 branch.

Discussion
----------

Moved 'contributing' images to their own directory

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.3+
| Fixed tickets | #3192

The PDF version of the "Contributing Guide" doesn't show the images (as reported in #3192). The rest of the PDFs correctly show them. Although I don't know the exact cause of the error, the "Contributing" guide images weren't stored in their own subdirectory inside `images/` and named after the book. That's the only difference between the right and the wrong PDF files.

For compatibility reasons I've left on purpose the original images at their location and just made a copy in the new directory.

Commits
-------

fc15b65 Moved 'contributing' images to their own directory
minor #4208 Added a note about the lacking features of Yaml Component (javiereguiluz)

This PR was merged into the 2.3 branch.

Discussion
----------

Added a note about the lacking features of Yaml Component

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes
| Applies to    | 2.3+
| Fixed tickets | -

In `symfony/symfony` repository there are a lot of issues reporting errors of the Yaml Component. These aren't errors but lacking features of the Yaml Component.

This PR tries to clearly state that Yaml Component lacks lots of features on purpose and provides a simple list of the most notable missing features.

Commits
-------

fe45194 Added a note about the lacking features of Yaml Component
minor #4205 replace "Symfony2" with "Symfony" (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
----------

replace "Symfony2" with "Symfony"

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | #4203

Commits
-------

3ba3d27 replace "Symfony2" with "Symfony"
minor #4215 Fixed code highlighting (WouterJ)

This PR was merged into the 2.3 branch.

Discussion
----------

Fixed code highlighting

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

 > Double quoted strings are the only scalar style capable of expressing arbitrary strings, by using “\” escape sequences.
 > - http://yaml.org/spec/1.1/#id904245

`\w` and `\d` are invalid escape sequences in Yaml, causing the Yaml highlighter to fail.

Commits
-------

f4b5dc6 Fixed code highlighting
Update Collection.rst

Wrong key in php code block.
minor #4216 Update Collection.rst (azarzag)

This PR was submitted for the 2.5 branch but it was merged into the 2.3 branch instead (closes #4216).

Discussion
----------

Update Collection.rst

Fixes wrong key in php code block.

Commits
-------

bf529bb Update Collection.rst
Merge branch '2.3' into 2.4

* 2.3:
  Update Collection.rst
  Fixed code highlighting
  Added a note about the lacking features of Yaml Component
  replace "Symfony2" with "Symfony"
  fix name of the Yaml component
  Moved 'contributing' images to their own directory
  add link to form testing chapter in test section