Add overwrite prompt

Users can now choose where to download the album to, although it's not
too sophisticated yet and needs plenty of work (pretty much just knocked
it up off the top of my head at 1am)

getur.pl
    - Users now have a prompt instead of mindlessly overwriting the
      album. It will definitely need tweaking, but it's enough for now.
    - Now using File::Path's mkpath for recursive directories. Album is
      saved in newpath/[albumname].