Remove upstream proxy support from TODO file

Upstream proxy support has been in place (though incomplete in the sense
that only "basic" authentication to the proxy is supported) for some
time now, so this item does not need to remain in the list of tasks to
be done.
Fix typo in README.rst regarding running Hydrogen

The README indicated that to run Hydrogen the command required was
"hydrogen_proxy.py". In fact, it is just "hydrogen_proxy".