Changed the visibility of some helper methods to private
Removed code duplication in the safeguards
Removed more duplication
Merge pull request #59 from stof/visibility

Changed the visibility of some helper methods to private
Merge pull request #61 from stof/remove_duplication

Removed code duplication in the safeguards
Used the stable version of Silex in the testsuite

Silex dev-master is now the dev version of 2.0, which is not BC. This bound constraint ensure the testsuite will not break once Pimple 2.1 is stable (which is the reason why Silex 2.0 was not selected yet)
Updated the driver for the Mink 2.0 API
Removed the BC layers for Symfony 2.2 and older