url_helper: read_file_or_url should pass headers param into readurl (#66)
Headers param was accidentally omitted and no longer passed through to
readurl due to a previous commit.
To avoid this omission of params in the future, drop positional param
definitions from read_file_or_url and pass all kwargs through to readurl
when we are not operating on a file.
In util:read_seeded, correct the case where invalid positional param
file_retries was being passed into read_file_or_url.
Also drop duplicated file:// prefix addition from read_seeded because
read_file_or_url does that work anyway.
