Using SonataClassificationBundle without SonataMediaBundle

- Using an explicit variable rather than calling the function "interface_exists"
fix Ambiguous class resolution, "Sonata\ClassificationBundle\Document\CollectionManager"
Update installation.rst
Merge pull request #34 from HotStep/patch-3

Update installation.rst
Introduce new DatagridBundle
Update SonataClassificationBundle.fr.xliff
Fix doc blocks
Merge pull request #36 from plouc/api_pager_support

Introduce new DatagridBundle
Update SonataClassificationBundle.fr.xliff

Correction
- 'Slud' > 'Slug'
- source-language="en"
Use PageableManagerInterface + Add unit tests on Managers + Only apply 'enabled' filter when corresponding criteria is passed
Merge pull request #37 from plouc/api_pagination

Use PageableManagerInterface + Add unit tests on Managers + Only apply '...
Merge branch 'master' of git://github.com/sonata-project/SonataClassificationBundle
Fatal error in CategoryManager

When making a call to getRootCategoriesPager or getSubCategoriesPager methods from the CategoryManager we obtain the following error:

ContextErrorException: Warning: Missing argument 1 for Doctrine\ORM\EntityRepository::createQueryBuilder()

The patch fixes this problem.
Revert "Using SonataClassificationBundle without SonataMediaBundle"

This reverts commit bf51e055b9764c3a984092add6d2984e3cdd993e.
Merge pull request #38 from zapoyok/categoryManager

Fatal error in CategoryManager
Merge pull request #33 from rmzamora/rz-patch-01

fix Ambiguous class resolution error
Merge pull request #35 from HotStep/patch-4

Update SonataClassificationBundle.fr.xliff
add support for Symfony 2.5 on travis
fix namespace