Merge pull request #1 from johnnyg/checkboxes

Add support for checkboxes / multiple answers
make selected answers an empty list if there's no userData
protect against undefined/null question entries
if it's not an array, correctAnswers becomes []
tidy up logic in selecting correct type for correct and selected answers
add back in object fallback (confused as to why it isn't converting properly)
only flag as multi if there's >1 entry
use typeof on strings (not instanceof String)
hack to check if is array. constructor references don't carry over between contexts
escape question text (HTML) and convert \n to <br>
text of questions is safe
(and now contains <br>)
this was supposed to be question text
use regex /g to replace newlines
enforce resizing on load
fix bug when you've deleted all the answers
fix
fix carrying forward of data
improve admin ui
fix typo
add select2 styles