Support React 0.11 and 0.12

This updates this package's `react` dependency to be either `0.11` or `0.12` since it works fine with either version of React.
Semver actively doesn't specify what versions under 1.0.0 mean, so basically it says you shouldn't trust them. In practice most "minor version" changes under 1.0.0 can be considered as major versions after 1.0.0. So assuming things will work throughout many `<1.0.0` releases sounds like a bad idea for things that will end up in production.