Summary:
Fixes#534:
```jsx
<SegmentedControlIOS
tintColor="#ff0000"
values={['One', 'Two', 'Three', 'Four']}
selectedtIndex={0}
momentary={false}
enabled={true}
onValueChange={ (value) => console.log(value) } />
```
This only supports string-based segments, not images. Also doesn't support full customization (no separator images etc); I figure this is a good MVP to lock-down a basic API
I also included a snapshot test case, but the images keep coming out funky. When I look at the sim, I see that the text labels show up for the selected segment, but the snapshot keeps coming out with no text on those segments. I tried forcing a delay, but same result. Is that explainable?
Obviously happy to change anything about the API, code-style nitpicks, etc
Closes https://github.com/facebook/react-native/pull/564
Github Author: Clay Allsopp <clay.allsopp@gmail.com>
Test Plan: Imported from GitHub, without a `Test Plan:` line.
Clay Allsopp
