CSS Custom Properties Should not be kebabified

[dmiller9911]

Currently if a user tries to overwrite css custom properties using aphrodite the key will run through kebabify, and could possibily end up with the wrong value.

Example:
###In

const styles = StyleSheet.create({
  item: {
    '--Some-Custom_Property': '#fff',
  }
});

Out

.item_someHash {
  ---some--custom_-property: #fff;
}

The issue lies in the kebabifyStyleName utility.