commentstree_q: Make it possible to skip updates for specific threads.
analytics: Don't send things with missing fullnames.

This fixes the "undefined-" item in fetch-trackers URLs. I believe I
brought on this bug by making .sponsorshipbox a placeholder even when
sponsorships don't exist.
analytics: (cleanup) Consolidate skip conditions.
analytics: Use deferreds to prevent duplicate fetch-trackers requests.
Change submit button text to say 'post' instead of 'link'
Move submit box above subreddit name/info/sidebar
Add a short README.
static Makefile: Work around NFS hardlink bug.