onDrop(file) {
    const reader = new FileReader();
    reader.onload = () =>{
        const fileAsArrayBuffer = reader.result;
        this.props.uploadFile(fileAsArrayBuffer);
    };
    reader.readAsArrayBuffer(file[0]);
  }

export const uploadFile = file => async dispatch => {
    const res = await axios.post('api/upload_file', file);
    dispatch({type: FETCH_OVERVIEW, payload: res.data.overview})
};