Fix incompatibility with pytest 3.7

[bakamitai456]

After I upgraded pytest to version 3.7, it cannot find any test in my project.

I look into pytest source code. I find out that the problem is the function pytest_pycollect_makemodule always return OdooTestModule object but in the original pytest source code it will check the path first. If the path is __init__.py it will return Package object.

[ddufresne]

@kosolart thank you, works for me

[guewen]

Released in 0.4.3