render question.stimulus
remove question.answer.value
rename exercise.background to exercise.stimulus
Merge pull request #5 from openstax/update-exercise-json

Update exercise json
Merge pull request #4 from openstax/all-tasks-have-steps

all tasks are generic and have steps
Merge pull request #3 from openstax/render-assignment

Render assignment with multiple steps
Merge pull request #1 from openstax/exercise-task

add an Exercise Task supporting multiple formats
Merge pull request #2 from openstax/math-render

Render Math
assume non-exercise steps have not been completed
refactor question stimulus & stem render to mixin
remove unnecessary double-quotes
use text area for short-answer questions
add font-awesome and some icons/styling
styling tweaks
Merge branch 'style-tweaks' into gh-pages