public function update(FileRequest $request, $id)
 {
     $date = Carbon::now();
     $file = File::findOrFail($id);
     if (strtolower($this->removeSpace($file->num_file)) != strtolower($this->removeSpace($request->input('num_file')))) {
         if ($this->exist($request->input('num_file'))) {
             return redirect()->to('expedientes/' . $id . '/edit')->withInput()->withErrors(array('invalid' => 'Ya existe el expediente por favor digite uno distinto'));
         }
     }
     $file->fill($request->all());
     $file->updated_at = $date;
     $file->save();
     return redirect()->route('expedientes.index');
 }