Converted decoders to return IO
Fetching/decoding now using filehandles.

- This is more efficient with memory.
Instantiate IO::Scalar properly
Parse data from IO objects.

- Saves a great deal of memory.
Allow feed_user and feed_password

- Was preventing them from making their way to the fetcher.
Save HTTP to a tempfile rather than buffer.

- Saves on memory usage.
Ensure that tempfiles are deleted on program exit.