Fix #6 - Retrieve rule list dynamically from gtfs-rt-validator library

[Suryakandukoori]

Summary:

Rule descriptions are dynamically pulled from edu.usf.cutr.gtfsrtvalidator.validation.ValidationRules and edu.usf.cutr.gtfsrtvalidator.api.model.ValidationRule

Expected behavior:

No change in behavior

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[barbeau]

Thanks @Suryakandukoori!