Merge pull request #128 from csmith/master

Download addons feed over HTTPS.
Update addon browser for addons.dmdirc.com move.
Merge pull request #129 from greboid/activewindowtests

Update addon browser for addons.dmdirc.com move.
Set versions on plugins properly.

This makes the plugins include their version in the output file
name, and when used as a dependency.

Also create a dist-versioned directory which accumulates versioned
plugins.