Deal with (usually old) distros that don't unpack nicely.

Some archives do not unpack into their own directory.  And
if by chance they only had one file, then this would expose
a bug.
Better warning about no changes.

This clarifies that the index did not change, but the
repository contents may have actually changed.  This is
rare, but it could happen if you add or pull a distribution
that contains no packages.
Warn about archives with no packages.

I thought we always did this, but I must have taken it
out at some point.  Stupid me.
Update installer to pull from the now semi-official Stratopan repository.
Merge branch 'master' of github.com:thaljef/Pinto into stratopan