Example for squashfs creation is not really valid

The examples/squashfs_create.go will not ever really be viable when doing proper error checking of returned values as it calls CreateFilesystem which will always return a filesystem.ErrReadonlyFilesystem for filesystem.TypeSquashfs.

If it is possible to properly create a writable squashfs the example should be updated to properly show how it is suggested to handle above error (I know how to check types of errors in go, I'm suggesting that the example should either note the error to check if it can be ignored in this case for creating a squashfs object)

[deitch]

Yeah, that is a valid point. We should have:

1. A new examples/squashfs_read.go that reads it via the way shown, and then use it to read something
2. The existing examples/squashfs_create.go that does it the way the tests do and successfully creates.

Want to open a PR to fix it?