Allow a user to upload a CSV for validation

[ldodds]

Provide a file upload option to allow a user to validate a CSV that hasn't yet been published to the web

[ldodds]

csvlint.rb now supports file validation, so the remaining piece for this is to add a file upload and/or text box to the csvlint app. File upload might be easier when working with larger files.

[ldodds]

csvlint.rb now supports file validation, so the remaining piece for this is to add a file upload and/or text box to the csvlint app. File upload might be easier when working with larger files.