Configurable option to parse the yaml erb files with the rails runner

[wassimk]

This plugin regex parses fixture YAML files. This usually works, but the fixture files are more than YAML files. They are ERB too. I've encountered cases where a Ruby loop is used to generate fixtures.

One fix for this is to use the Rails runner to process the ERB and output only YAML. A downside to this is the documentation window will show the final YAML output, it's more helpful to see the ERB. Another option is to improve the regex.