new post on resque, retrying, and idempotence

A reaction to [this post](http://eng.joingrouper.com/blog/2014/06/27/too-many-signals-resque-on-heroku/), where they have the same problem as us, but, in my opinion, solved it the wrong way.

This is bit technical but hopefully in the "this team knows its shit" category.
Would it make sense to add a header to this section, and more specifically call it out as an example of how to make a job idempotent? Like, "Here's an example of how we've done this for a background job. Blah blah blah".

The reason I say that is since this goes into a bit of detail about how the charging job is implemented to be idempotent, it felt a little like the focus of the article became how to specifically make a job that charges money idempotent, rather than a general article about why idempotent jobs are good and why use should build jobs that way. More clearly isolating this detail as an example might make that focus more clear.