How to handle file picker in React

Issue #190

render() {
  <Button color="inherit" onClick={this.onImagePress} >Image</Button>
  <input ref="fileInput" type="file" id="myFile" multiple accept="image/*" style={{display: 'none'}} onChange={this.handleFiles}></input>
}

onImagePress = () => {
  const fileInput = this.refs.fileInput
  fileInput.click()
}

handleFiles = (e) => {
  e.persist()
  const file = e.target.files[0]
}