Fixed more touch-related Orderer breakage

Summary:
Orderer no longer removes cards with unbound events by not adding
event handlers to cards that are currently animating. Additionally, you'll
no longer get any JavaScript errors if you tap on a card bank while another
card is animating back into position.

Test Plan:
- Run Perseus on a touch device.
- Create an Orderer ([shortcut](http://localhost:9000/test.html#content=%7B%22question%22%3A%7B%22content%22%3A%22%5Cn%5Cn%5B%5B%E2%98%83%20orderer%201%5D%5D%22%2C%22images%22%3A%7B%7D%2C%22widgets%22%3A%7B%22orderer%201%22%3A%7B%22type%22%3A%22orderer%22%2C%22graded%22%3Atrue%2C%22options%22%3A%7B%22options%22%3A%5B%7B%22content%22%3A%22%24x%24%22%7D%2C%7B%22content%22%3A%22%24y%24%22%7D%2C%7B%22content%22%3A%22%24z%24%22%7D%5D%2C%22correctOptions%22%3A%5B%7B%22content%22%3A%22%24x%24%22%7D%2C%7B%22content%22%3A%22%24z%24%22%7D%5D%2C%22otherOptions%22%3A%5B%7B%22content%22%3A%22%24y%24%22%7D%2C%7B%22content%22%3A%22%24z%24%22%7D%5D%2C%22height%22%3A%22normal%22%2C%22layout%22%3A%22horizontal%22%7D%7D%7D%7D%2C%22answerArea%22%3A%7B%22type%22%3A%22multiple%22%2C%22options%22%3A%7B%22content%22%3A%22%22%2C%22images%22%3A%7B%7D%2C%22widgets%22%3A%7B%7D%7D%2C%22calculator%22%3Afalse%7D%2C%22hints%22%3A%5B%5D%7D)).
- Place a few cards in the live area.
- Open up the console.
- While a card is animating back into position, click on it. Notice that there are no warnings.
- While a card is animating back into position, click on any bank card. Notice that there are no errors.

Reviewers: jack

Reviewed By: jack

Subscribers: eater, alpert

Differential Revision: http://phabricator.khanacademy.org/D9516