TinyMCE Editor for Course Updates and Handouts

Feel free to test it out @stvstnfrd @caesar2164 @dcadams
This is confusing. At least, drop the paren down to a newline. Can you
also put the two keys on separate lines?

```javascript
CourseInfoHelper.editWithTinyMCE(
    base_asset_url,
    this.$('.handouts-content-editor').get(0).id
);
```