Merge pull request #40 from chives/dev

Fixed bad container parameter
Merge pull request #41 from chives/dev

Updated installation doc
Make removable file checkbox unrequired by default
Updated spec
Merge pull request #42 from bartekgruszka/fix-removable-checkbox-required

Make removable file checkbox unrequired by default
Upgrade sensio/framework-extra-bunlde to ~3.0