support ie9.
rebuild files.
don't use flexbox for tutorial simulator layout.
make weather-outfit.js work w/ tutorial.
regenerate files.
make debug panel work on IE9.
regenerate files.
add debug mode to tutorial.
use <h2> for section debug headings.
show both complete/incomplete challenge areas in debug mode.
move styles into tutorial/styles.css.
fix some HTML tag errors.
only assign window.baseURL if it's not already defined.
added bin/export-tutorial.js.
force intra-document links to open in same window.
added sections on sharing the app, changing a single picture.
mention placement of sign in button.
shorten copy in 'put some clothes on that webpage' section.
fixed up copy in 'adding our own recipe'.
make arguments/return value explanation interactive.