Inline Analytics

  Display of answer distribution graphics inline on the problem page
  for instructors.

  Problem types supported for graphics:
    - MultipleChoiceResponse
    - ChoiceResponse

  Problem types supported for line item display:
    - OptionResponse
    - NumericalResponse
    - StringResponse
    - FormulaResponse
    via setting

Internal review only for now.
This needs to be a named function. As is, this creates an anonymous
function and assigns it to `process_response`. Since this variable is
not explicitly declared, it leaks into the global namespace. This syntax
is also missing a semicolon to end the assignment statement.
This should be changed to:
```javascript
function processResponse(response, partsToGet, questionTypes, correctResponses) {
    // ...
}
```

Named functions provide a better stack trace to ease debugging. You also
don't need a semicolon after the declaration ;)

While you're changing that line, can you change the function name as
above to follow the JavaScript/JSON standard camelCaseStyle? I won't add
the same comment every where else snake_case_style is used here, but it
_does_ make it a bit easier to parse mentally when style is consistent.
That and the whole "code should look like it was written by a single
person" sort of thing. Up to you