convert to emotion

Summary:
My benchmarks have shown react-emotion to be faster than the current implementation of `styled`. For this reason, I am converting all styling to [emotion](https://emotion.sh).

Benchmark results:
{F136839093}

The syntax is very similar between the two libraries. The main difference is that emotion only allows a single function for the whole style attribute, whereas the old implementation had functions for every style-attirbute.

Before:
```
{
  color: props => props.color,
  fontSize: props => props.size,
}
```

After:
```
props => ({
  color: props.color,
  fontSize: props.size,
})
```

Reviewed By: jknoxville

Differential Revision: D9479893

fbshipit-source-id: 2c39e4618f7e52ceacb67bbec8ae26114025723f

src/chrome/ErrorBar.js

@@ -7,7 +7,7 @@
 
 import {styled, colors} from 'sonar';
 
-const ErrorBarContainer = styled.view({
+const ErrorBarContainer = styled('div')({
   backgroundColor: colors.cherry,
   bottom: 0,
   color: '#fff',