news for selectizeInput()
factor out the code to determine which options should be evaluated into a utility function checkAsIs(), so that it can be applied to selectizeInput() as well
apply checkAsIs() to selectizeInput(), and store the names in data-eval in the script

note we switched the order of {} and config.text() in $.extend(), so that users can overwrite the default options like labelField, valueField, ...
it is safer to evaluate the string inside ()

e.g. one cannot directly evaluate {a: 1, b: 2}, although it is legitimate JSON; eval("({a: 1, b: 2})") always works
add a note about the I() options in selectizeInput()