clean up code
changes in README.md
moved FileNotFoundError into new compat module to make it available for import
Merge pull request #123 from xrotwang/refactorDataAccess

moved FileNotFoundError into new compat module
Merge remote-tracking branch 'upstream/master'
adjust filenotfound error
Merge pull request #124 from LinguList/master

Clean up code in model.py, derive.py, and setup.py