message: Added selectedItem to props.renderButton args.  Combined args into single object so users can use argument destructing instead of having to track all method arguments.  Added getSelectedItem helper function.  Added propType for renderButton.
diff: @@ -72,6 +72,10 @@ class PickerNB extends Component {
  return _.get(item, 'props.label');
  }
  + getSelectedItem() {
  + return _.find(this.props.children, child => child.props.value === this.props.selectedValue);
  + }
  +
  modifyHeader() {
  const childrenArray = React.Children.toArray(this.props.headerComponent.props.children);
  const newChildren = [];
  @@ -94,7 +98,7 @@ class PickerNB extends Component {
  const onPress = () => { this._setModalVisible(true); };
  const text = this.state.currentLabel ? this.state.currentLabel : this.props.defaultLabel;
  if (this.props.renderButton) {
  - return this.props.renderButton(onPress, text, this);
  + return this.props.renderButton({ onPress, text, picker: this, selectedItem: this.getSelectedItem() });
  }
  return <Button
  style={this.props.style}
  @@ -175,6 +179,7 @@ PickerNB.Item = React.createClass({
  PickerNB.propTypes = {
  ...View.propTypes,
  + renderButton: React.PropTypes.func
  };
  const StyledPickerNB = connectStyle('NativeBase.PickerNB', {}, mapPropsToStyleNames)(PickerNB);
  