Email admins with the full 500 email

Fixes the lack of debugging information from the custom error email generated by jsonview.

This fix generates the normal error email Django sends when a 500 occurs, which includes:
- Path of request
- Additional request meta information (GET, POST, META, etc)

These make the exceptions easier to debug.

![jsonview](https://cloud.githubusercontent.com/assets/59689/3623230/9239e426-0e49-11e4-9dd6-38d4481fc0a1.png)

This can just use `logger.exception`, right?