Fix setuptools 20.2+ compatibility
Fix setuptools 20.2+ compatibility

Fixes #686

kkopachev/thumbor,kkopachev/thumbor,abaldwin1/thumbor,scorphus/thumbor,davduran/thumbor,abaldwin1/thumbor,kkopachev/thumbor,okor/thumbor,marcelometal/thumbor,gi11es/thumbor,davduran/thumbor,fanhero/thumbor,scorphus/thumbor,BetterCollective/thumbor,marcelometal/thumbor,voxmedia/thumbor,fanhero/thumbor,voxmedia/thumbor,fanhero/thumbor,thumbor/thumbor,abaldwin1/thumbor,BetterCollective/thumbor,thumbor/thumbor,thumbor/thumbor,Bladrak/thumbor,scorphus/thumbor,Bladrak/thumbor,okor/thumbor,gi11es/thumbor,kkopachev/thumbor,fanhero/thumbor,davduran/thumbor,abaldwin1/thumbor,scorphus/thumbor,thumbor/thumbor,davduran/thumbor,BetterCollective/thumbor,okor/thumbor,voxmedia/thumbor,gi11es/thumbor,marcelometal/thumbor