Document and polish pic module.
update docs.
Make player and example use new Image class as return for get_frame instead of old output.
Update writer and tools to use the new Image class.
Restore image avframe to original values after write.
Return the total size written so far in write_frame.
Update docs.
Add get image size func, update docs.
Bump to 3.0 because of API changes with pic addition. API should now be stable.
Bump to 3.1-dev.