Remove visualizer comments.
Allow the readme to not have to be checked in.

This makes development easier in that the user teacher does not have to commit the readme to view output.
Remove no longer needed 'first_commit' logic.
Model steps rather than commits.

This focus allows commits to be an optional data payload on a step. Solves the issue where not all steps would need or want a commit.
Serve local js libraries when in development.
Remove the file tree visualizer.
Remove prev-next bottom.
Remove table of contents rendering.
Revise layout to two columns.
Remove table-of-content js logic and views.
Refactor updateStep to trigger as part of stepView render();
The steps should be based on commits.

Previously the steps were based on the readme chunks. If the readme is not done then we can't navigate through our commits while we are creating the readme.
Use location.hash change instead of real step url.

it's easier.
Small visual update.
Add file content view at commit.

This allows the user to copy and paste the current state of the code for his own use.
Remove unused d3.js.
Update design to dark theme.
Add start over button.
Change urls to support username namespace.

Mock my 'plusjade' account.
Add segment.io tracking.