Update to react v15.0 about react-split-pane

[kachkaev]

Found at least one thing to change after upgrading to React 15.

This warning comes out when defaultSize is saved to and then read from LocalStorage:

warning.js:44 Warning: a `div` tag (owner: `Pane`) was passed a numeric string value for CSS property
`width` (value: `298`) which will be treated as a unitless number in a future version of React.warning
@ warning.js:44dangerousStyleValue

Easy to fix:

defaultSize={ localStorage.getItem('splitPos') }

↓

defaultSize={ parseInt(localStorage.getItem('splitPos'), 10) }

[tomkp]

I've pushed the change to the readme. Is this issue Ok to be closed now?
Thanks

[kachkaev]

React is 15+ since 36eb246. @tomkp could you please update that example with localStorage in README.md (see above)? We can then close this issue.