0.4.0

Bugfix:

• Fix the validation view with mandatory file (#140)

Minor fixes:

• A few typo fixes in documentation (#128).
• Added a Makefile autodocumentation (#127).
• Added a tox target to build documentation (#130).
• Fix autodoc generation (#131).
• Added flake8 checks via tox (#133).
• Added tox posargs to pass extra arguments when running tests (#135).
• Solve setup.py install "zip" error. Skip global package installation (#139).
• Moving check-python-imports test to the tox file (#138).