add tutorial link type
tutorial feedback
updated feedback icon
set RSTUDIO_HTTP_REFERER
Revert "set bg = transparent for graphics device; turn off shadow device for newPage"

This reverts commit 194e20d1a8b03e7249fb671d89a3ee405d1053f3.
include Request-Method in custom http requests
only check for graphics changes in the background if our device is active
stubs for quiz renderer
add filterString utility to regex utils
use namespace alias for boost::algorithm
initial work on slide quizzes
add username to presentation log
more permissive regex for capturing quiz items
refine === completion in r markdown
refinements to quiz feedback layout
add images to quiz feedback
refine quiz feedback ui
more tweaks to feedback region
change field name: correct -> answer
add threadsafe map class