bump version to 6.3.1
bump version to 6.3.1

marcelometal/thumbor,voxmedia/thumbor,marcelometal/thumbor,thumbor/thumbor,thumbor/thumbor,marcelometal/thumbor,gi11es/thumbor,gi11es/thumbor,thumbor/thumbor,scorphus/thumbor,voxmedia/thumbor,scorphus/thumbor,kkopachev/thumbor,voxmedia/thumbor,kkopachev/thumbor,kkopachev/thumbor,scorphus/thumbor,okor/thumbor,thumbor/thumbor,gi11es/thumbor,kkopachev/thumbor,okor/thumbor,scorphus/thumbor,okor/thumbor