Dank Software Depot 1.1.4

Thanks to @qu33rz for reporting #13.

• Updating system packages on Arch works. The transaction resolved package
  names against the sync databases exactly as they sit on disk, and nothing in
  this plugin ever refreshed them — while the list of pending updates comes
  from checkupdates, which refreshes a private copy of those databases and
  throws it away. So the list was right, the transaction was resolved against
  yesterday's answer, libalpm replied "is up to date -- reinstalling" for every
  package, and the check afterwards correctly reported that nothing had reached
  its new version. The databases are refreshed before a transaction now
• A package already at the version the repositories offer is left alone,
  which is what pacman's own --needed does and what the daemon's pacman -Syu has always used. Those reinstall-the-same-files lines are gone
• A failed refresh — one unreachable mirror — is a reason to attempt the
  transaction with what is on disk, not to refuse it, and the reason travels
  with the result either way
• The Arch path now has a test, run against a stand-in for pyalpm, so it is
  checked on machines that have neither pacman nor Arch — which is every
  machine this plugin is developed on

One thing to know on Arch: updating a single package refreshes the databases
first, which makes it a partial upgrade — the thing Arch tells you not to do.
Update All sends the whole pending list and is the safe path. Arch support is
still marked experimental for reasons like this one.