Merge pull request #7 from josegonzalez/master

Pluginize cache engines
Add composer.json
Update README with composer installation

Move Licence to MIT-LICENCE file
Update changelog
Fix readme code formatting
Fix missing comma
Use `Memcached::getAllKeys` to retrieve list of cached keys
Adding groups support

Rename remaining memcache instance as memcached
Add test
Update changelog
Add travis, coveralls and editorconfig
Add CI badge
Properly set sasl authentication information