FIX: Transform Sentiment classification before saving

[romanrizzi]

We were storing the classification result in a slightly different format:

[{"label"=>"positive", "score"=>0.830914}, {"label"=>"neutral", "score"=>0.16409673}, {"label"=>"negative", "score"=>0.0049892818}]

when it should be:

{"neutral"=>0.52367204, "negative"=>0.014189002, "positive"=>0.46213892}