Added fix to io_utils.list_files function for instances where column …

[bryjcannon]

Addresses issue #41

[coveralls]

Pull Request Test Coverage Report for Build 7426002544

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.06%) to 96.465%

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Totals
Change from base Build 6947912800:	0.06%
Covered Lines:	439
Relevant Lines:	451

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💛 - Coveralls

[bryjcannon]

I updated the load_folder test before merging - I changed the test as the original version was essentially forcing the error this pr addresses to exist. I think the updated test aligns more with what we want but want to quickly chat before the merge is confirmed.

[alex-l-kong]

@bryjcannon just to be safe, I added more test cases to encompass the specific issues you were running into.

[bryjcannon]

Awesome thanks!