File storage tests

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Link storage tests

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
PEP8 and PEP257 improvements

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Merge pull request #7 from jirikuncar/tests-and-improvements

File storage tests