To create data for testing (warning, this takes a long time and requires
a ~64GB download, and ~200GB of hard drive space):

$ mkdir metadata
$ cd metadata
$ wget http://dumps.wikimedia.org/enwiki/latest/enwiki-latest-md5sums.txt
$ cd ..
$ ruby md5_to_links.rb
$ mkdir data
$ ruby get_data.rb
$ ./parse_data.sh