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

[Suryakandukoori]

Summary:

Retrieve rule list dynamically from edu.usf.cutr.gtfsrtvalidator.lib.validation.ValidationRules for the Excel file "Rules" tab.

Expected behavior:

Pull rules dynamically from edu.usf.cutr.gtfsrtvalidator.lib.validation.ValidationRules each time

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• [X] Run the unit tests with mvn test to make sure you didn't break anything
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[barbeau]

Thanks @Suryakandukoori!