On re-select the text-input the first option of the list gets selected by default

[tanmay-cs13]

Function _onTextEntryUpdated should be update to set the selectionIndex equal to null.

  _onTextEntryUpdated: function() {
    var value = this.refs.entry.value;
    this.setState({visible: this.getOptionsForValue(value, this.props.options),
                   selection: '',
                   selectionIndex: null,
                   entryValue: value});
  }