Do not rely on extension when reading images

[jose1711]

Do you want to request a feature or report a bug?

Feature

What did you expect to see?

It would be nice if performous does not rely on filename extension when reading image. Currently if it finds a JPG file named album.jpg it tries to read is as PNG and (presumably) gives an error:

libpng error: Not a PNG file
image/error: Reading PNG failed

[ooshlablu]

FWIW this is still an issue. I have to do a manual find and file and name them accordingly.