Sifo 2014-12-21

Source: http://www.tns-sifo.se/media/527300/vb_dec_2014_svd.pdf
Add missing `uncertain` data for Sifo 2014 polls

Source: http://www.tns-sifo.se/media/527300/vb_dec_2014_svd.pdf
Merge pull request #29 from urdh/december-polls

Sifo 2014-12-21