Moodle-dl

Fixes
- Because Moodle now does no longer allow cross-origin access, we now use font awesome from another cdn. This probably does not fix all Errors in Quizzes and Lessons HTMLs, please report more errors.

Bug Fix
- Fix crash if no calendar was downloaded before

Added
- You can now download course calendar events. moodle-dl generates a simple HTML for every event. Initialy it will download all events, then it loads only events that are created after the last modification of events. To activate this set `download_calendars` to true.
- You can now deactivate downloading of book mod, use option `download_books`.

Fixes
- Create table of contents recursive with subchapters

Added
- Now the book mod can be downloaded, we generate a simple table of contents for every book

Changes
- From now on, I try to follow semantic versioning.

Just fix the URL to https://github.com/C0D3D3V/Moodle-DL/wiki/Example-Config.json-and-Options in the Readme