Disabled Travis build for feature branches

Given that all feature branches have a PR which gets build by Travis, it is useless to build the branches as well.
Merge pull request #29 from Gaufrette/optimization/travis-config

Disabled Travis build for feature branches
AdapterInterface based on file

AdapterInterface based on file

Fix filesystem

Fix phpspec
AdapterInterface now uses FileInterface
Merge pull request #30 from Gaufrette/feature/adapter

AdapterInterface based on file
Restore legacy utils