index used as key

[ZooeyMiller]

Indexes shouldn't be used as keys in react as it doesn't work properly for react's diffing.

Tonnah/src/components/board/photogroup/photogroup.js

Line 12 in c657af9

key={urls.indexOf(url)}

this video explains it better than I ever would: https://egghead.io/lessons/react-use-the-key-prop-when-rendering-a-list-with-react

(ping me on gitter if you need the fac egghead login)