config: Update to mailing list info in pelicanconf.py.

Thanks to Freddy Martinez for pointing this out. The link to the
mailing list in the footer was pointing to our old Google Group.
I've set a new link to point to our announce list and to our
discussion list.
add: Added new page to display SRPMS. gitignore hides source files.

I'm using this page to store SRPMs for a COPR repository. However,
I don't want to include the actual SRPMs in git. The page and the
links will be stored in git, but the SRPMs will only be on the
website.