Fix date parsing to allow proper sorting by date

* This will not parse ALL possible date formats, but works so far
Adds a logo
Update go-pkg-rss submodule commit ref
Remove need for forked version of go-pkg-rss

* This removes the need for a git submodule, etc.
* Unfortunately, this also (temporarily) breaks the rendering of dates
client-side
Replace relative go-pkg-rss import with absolute url

* This is part of the goal of moving away from submodules
Remove go-pkg-rss submodule (no longer need forked version)