Feature: Visualize failed webhook deliveries for the entire instance

[larsxschneider]

Calculate and visualize the number of failed webhook deliveries per day:

cat /var/log/hookshot/resqued.log.1 | grep -e '^\["repository-' | wc -l

[toddocon]

This is cool! Just ran it on my instance. To be really useful we'll need a table which shows totals for each url or maybe determine the ORG/repo for the failed call. Totals for the calls would be helpful.