Merge pull request #25 from nmferraro5/master

Unknown_None for Clinical Sequencing
Clean names of generated cells for checkbox_mutex

Options can include odd characters like slashes that we don't want to use in the field names because redcap probably won't handle it.
Adding contributors file.
Add value_with_range
Added link to wiki in README
Wiki link renamed
Handle commas in answer choices
Indexing bug fixed