Bumping rmagick version to 2.13.2, since it fixes a troublesome issue
with building rmagick's extensions on OS X when imagemagick was installed
via homebrew.

See also: https://github.com/rmagick/rmagick/commit/b8e690abc42474373bb6c513787f6117751d0e1b
Added a "view in gallery" link to the paintings partial - it opens a
fancybox viewer that treats the collection of uploaded images as a
single gallery.