Implemented own extends of Filesystem and FilesystemInterface to comply with type inspection until new major version
Comply to coding standards
Fixed 'The closing brace for the interface must go on the next line after the body'
If using the read method instead of get, we can use it directly
Read can also return false, so return null when content cannot be read
Invalid type check fixed
Merge pull request #50 from dennisdegreef/fix49

Implemented own extends of Filesystem and FilesystemInterface to comply...