Fix upload URL to be /image instead of /upload
Fix upload URL to be /image instead of /upload

https://github.com/thumbor/thumbor/wiki/How-to-upload-images and http://thumbor.readthedocs.org/en/latest/how_to_upload_images.html state it's `/image`.
abaldwin1/thumbor,okor/thumbor,scorphus/thumbor,voxmedia/thumbor,gi11es/thumbor,kkopachev/thumbor,scorphus/thumbor,gi11es/thumbor,Bladrak/thumbor,marcelometal/thumbor,abaldwin1/thumbor,voxmedia/thumbor,davduran/thumbor,thumbor/thumbor,abaldwin1/thumbor,fanhero/thumbor,fanhero/thumbor,fanhero/thumbor,davduran/thumbor,thumbor/thumbor,davduran/thumbor,marcelometal/thumbor,okor/thumbor,marcelometal/thumbor,gi11es/thumbor,davduran/thumbor,voxmedia/thumbor,fanhero/thumbor,abaldwin1/thumbor,kkopachev/thumbor,Bladrak/thumbor,okor/thumbor,kkopachev/thumbor,scorphus/thumbor,scorphus/thumbor,thumbor/thumbor,kkopachev/thumbor,thumbor/thumbor