Minor fixes in icon resolution

MS tiles for Win 8.1 and 10 match recommendations (see https://msdn.microsoft.com/library/dn455106(v=vs.85).aspx)

Add command-line access

Fix multi source config

Coast was being set twice and windows was not set at all.

Fix bug where, if you weren't generating all icon formats, you couldn't
use a multiple sources configuration.

checks for 2xx codes and sends original error message

monkeypatch unzip.Parse.emit() to emit single 'end'