Fix Issue #92

Close #92

Overview

• Fixed version information for easy access
• I implemented __version__ style with reference to yapf from google. ( cf. google/yapf )

What I checked

• All tests are green
• I can access version via ffmpeg.__version__

Resources

See:

• https://github.com/google/yapf/blob/main/setup.py
• https://github.com/google/yapf/blob/main/yapf/__init__.py