Create a browser lesson

[donkirkby]

Similar to the start and goal files that PyCharm's live turtle supports, try to make a browser lesson based on some of the early lessons in the Python tutorial.

• [x] Parse and display markdown source with editor for code blocks.
• [x] Trigger onChange() event.
• [x] Load markdown from JSON file based on queryParam.
• [x] Display output.
• [x] Compare goal with output. (Put goal code in same code block.)
• [x] Add progress bar.
• [x] Apply a theme to the page, maybe Bulma?
• [x] Add a reset button that puts source code back to start.
• [x] Start a table of contents for lessons on default lesson.
• [x] Add an options section: first option is to disable live coding for REPL code samples. Declare option with ### static ###.
• [x] Detect REPL code samples by looking for ">>>" and disable live coding. Force live coding with ### live ###.
• [x] Rename "lesson" to "tutorial".
• [x] Link to tutorial source folder from edit link at bottom of page.