Add .tsv files to allowed upload types

[aferriss]

Hey! I was wondering if we could add .tsv (tab separated values) files to the allowed upload types. I guess it's not that common a filetype but I just had one today and realized I couldn't use it. Any reason not to aside from just being cautious about what was allowed (like in #630)

Nature of issue?

• Found a bug
• Existing feature enhancement
• New feature request

[catarak]

no reason not to include it! this should definitely be added in.