Replaced deprecated method withLoaderManager in CustomGalleryActivity

This code was not from me. It was originally written by yusufsaber
mostly, and zokipirlo. I also changed min sdk to 11 from 7 because the
implementation added to this class needs it. You can read about it more
here: https://github.com/luminousman/MultipleImagePick/issues/8

I noticed the code did not have yusufsaber and zokipirlo's contributions that they brought up, so I figured maybe I could create a pull request from their code?