Bump to 6.0.0b4
Bump to 6.0.0b4

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