Search by regex

A common use case, when using Cleaner is that I want to sift the failed queue for various things, e.g.:
1.  Arguments which take specific forms.
2.  A message in the backtrace.
3.  A job which failed on a specific process.

To make this easier for me, I've thrown together a PR which enables the user to search the failed queue, via regex, for jobs that I care about.  I've also made a console helper method, `select_by_regex`, which lets the user do this via the command line.  I'm currently testing this on my systems at work, but I'd like to be able to contribute it back to the community.

So, the purpose of this PR is to get the ball rolling to see if this would be beneficial to others who use this gem.

TODO:
- [x] Update the README to show how to use the new functionality
- [x] Make the UI more pretty.