Added option for displaying avatar/skin from a remote server.
Examples:
http://minepic.org/url/skin/512/http://www.minecraftskins.com/newuploaded_skins/skin_20130511052059133169.png
http://minepic.org/url/avatar/512/http://www.minecraftskins.com/newuploaded_skins/skin_20130511052059133169.png