Fix schedualing time to 12 Hour format and extend "subject" field length.

#5479 

This PR fixes the event registration form issues from the issue above.

1. This problem was partially taken care of in https://github.com/openscholar/openscholar/issues/5392#issuecomment-38605511 (the error block). The bottom line of the captcha field is now fixed:
![selection_208](https://cloud.githubusercontent.com/assets/4497748/3076654/d58f10f2-e3f1-11e3-87b1-ebc5df9a2c00.png)

2. AM/PM in the scheduling times:
![selection_209](https://cloud.githubusercontent.com/assets/4497748/3076655/047f8a18-e3f2-11e3-87a6-fd8087fd2935.png)

3. Longer "Subject" field:
![selection_206](https://cloud.githubusercontent.com/assets/4497748/3076656/10ad7bb0-e3f2-11e3-91d1-b8ab286a1889.png)