from exiftool to exifread python lib and use location data

[jaakla]

Should fix https://github.com/andrewning/sortphotos/issues/115

[jaakla]

#116 simple fix is included here, as separate commit.

[andrewning]

I like the idea of only having python but (I may be wrong) exifread seems to not have the same level of capabilities as exiftool. From a quick test some of the file formats didn't work and some of the filters and recursive search options also seem to be lost.