Update question/answer content & grammar
Add togglePrevBtn method to handle all the logic of showing/hiding the previous button
De-lint, spacing, alignment, etc
Surround with closure to prevent leaking into global namespace
Indentation :\
Use single-quotes for strings (mainly so double-quotes can be used for DOM elements)
Use .on() instead of .bind()
Write all questions to DOM at once
Remove unneeded jQuery call
Determine correct answer index by correctAnswer property rather than by current index