Check for 404s when iterating through repo list

[pdurbin]

To prevent issues like #19 we should make sure we get at 200 response for each repo in github.tsv.

For now we can use this script:

#!/bin/bash
while read url; do
  curl -s -o /dev/null -I -w "%{http_code}" $url
  echo " $url"
  sleep .2
done < github.tsv

It'll show output like this:

200 https://github.com/berkmancenter/amber_apache
200 https://github.com/berkmancenter/amber_common
200 https://github.com/berkmancenter/amber_drupal
...