Merge pull request #5 from mente/options

options for memcached, thanks to mente.
Merge pull request #6 from mente/options

restored symfony 2.0.x compatibility
Fixes to make SMMemcached compatible with Symfony 2.0.
Deleted version name in composer.json
Merge pull request #7 from francisbesset/patch-1

Deleted version name in composer.json