Update introduction.rst

Console component is in symfony/console package, not symfony/config.
Merge pull request #404 from gregquat/2.4

Merging #403 from 2.3
Merging #401
Merge pull request #405 from gregquat/2.3

Merging #401
Merge pull request #406 from symfony-fr/2.3

Merging #401
Merge pull request #401 from FGM/patch-1

Update introduction.rst
Update text of links

Update text of links in "Tester les commandes" chapter
Merge pull request #412 from mathias-strasser/patch-1

Update text of links