Style dropdown (so visible) and flash message so as not to run into logo.
Improve displaying error messages.
Delete cruft error flash notice method.
Add active link from class and setup for has_many through.
Change join table name, now site functioning again.
Add planets/galaxies lab classwork.
Revised HMT, but does not *work*. Also, replaced category images with SVG files, also non-functional. Yay.