Stop coffeescript mode from crashing

Coffeescript mode is crashing under node for us.

It's not clear if this is the right patch, but the issue is that this line expects a `mode` object: https://github.com/codemirror/CodeMirror/blob/cd17bae3716459028ec973cb2c9511834d978afb/mode/coffeescript/coffeescript.js#L194