Add travisCI build status image
Mod: fix max APCu version
Merge pull request #6 from M6Web/feature/APCUversion

Set max APCu version
Fix: typo
Mod: use atoum bootstraping
Fix: APCu API was update to follow APC API (https://github.com/krakjoe/apcu/issues/50)
Mod: fix minimum APCu extension version