Fix for htmlbooks

Htmlbooks were not updated in https://github.com/edx/edx-platform/pull/3744/files. This PR makes the relevant changes:
1. Passes storage_url and token to StudentNotes init.
2. Adds tinymce.js to the template since it is no longer being included globally.

Tests will be added later.
Not needed if only one version of tinymce is being used everywhere.