There's a breakdown of their spending in their S-1 filing [1], under Consolidated Statements of Operations.
According to this, they could be profitable if they wanted to be, but they are using their profits and re-investing in growth.
E.g. they more than doubled their spending on marketing from $17.8m to $39.6m from 2013 to 2014.
[1]: http://www.sec.gov/Archives/edgar/data/1370637/0001193125150...