Evaluates code solution

WARNING! CHANGE NOT MERGED ON PURPOSE. This is a dangerous change. 

It allows the application to evaluate the respondent's actual computer code and thereby allow people to provide a coded solution to the problem, 

BUT I was able to issue commands to my terminal through the solution entry box. 

I'm not kidding. Try it with the following: `say "hello"` (include the backticks).

That's clearly dangerous. Imagine if someone typed rm -rf in there. They could delete the whole host computer. 

I'm researching how to make this secure, but at the moment it's not. That's why this change is not merged yet.