Cleanup cucumber tables (and automate the process)

@kevgo 

Add a script to cleanup and lint cucumber tables.

No longer need to properly indent cucumber tables by hand. Just update the table with the proper data and run  `bin/clean_cucumber` which will indent and align the tables properly. Added a linter as well so you committing an ill-formatted table will cause the build to break (it will tell you to run `bin/clean_cucumber`).
Very cool! I have a Vim plugin that formats tables properly as I write them. But yeah, it was super painful before I had that!

I think extracting this as a gem would be good because then we can unit test it better as well.