Display excludeable file types and validate

[danielingegneri]

First pull req, plz let me know if needs work. #170

[kehoecj]

@danielingegneri Thanks for the PR! Love the implementation. Looks like there is a goreportcard issue around the complexity in the *excludeFileTypesPtr - please take a look an see if you can resolve.

[danielingegneri]

Attempted to reduce complexity. Mostly by simplifying validation more. Also noticed the messages being printed on validation error, and the error being returned, were repeats. Suggest instead displaying the error text in thrown error.
EDIT: Unfortunately can't get complexity below 17 without refactoring more of that function. Complexity seems warranted for the number of variables being validated.

[danielingegneri]

Is it preferred that I undo the additional logging changes made, and keep to minimum?

[kehoecj]

Attempted to reduce complexity. Mostly by simplifying validation more. Also noticed the messages being printed on validation error, and the error being returned, were repeats. Suggest instead displaying the error text in thrown error. EDIT: Unfortunately can't get complexity below 17 without refactoring more of that function. Complexity seems warranted for the number of variables being validated.

@danielingegneri I'm willing to push your change for now and deal with refactoring later to get the complexity down a bit. Let me do a final review and if everything looks good I'll merge it.

[kehoecj]

@danielingegneri Let me know when this is ready for another review. Looks like a merge conflict and just one comment needs to be resolved before we can merge this in

[danielingegneri]

I've sorted the list, added space after comma, does look nicer now :)