Allow reading from stdin and sockets

[oshyshko]

I'd like to use imageReader to get frames from stdin.

Perhaps, a generic way of reading from any System.IO.Handle would be even better.

Maybe, something like this:

import System.IO (Handle)

data InputSource = File FilePath
                 | Camera String CameraConfig
                 | InputHandle Handle
                 deriving (Eq, Show) -- System.IO.Handle doesn't have instances for Read and Ord

Or is there another way to read from stdin?