Bourbon's box-shadow mixin has been deprecated, and they recommend to use the
official spec.

The official border-radius mixins were deprecated and removed in Bourbon 3.0.
https://github.com/thoughtbot/bourbon/pull/95

- removed ::selection css from reset.scss
- removed variables from variables.scss
- removed variable calls from course/base/base.scss and base/base.scss

Stanford got some feedback from our students/faculty that students
were making accidental clicks on radio-button capa questions.
They would click way to the right of the label text, but it would
still select the corresponding input, which caused some students
to make unintentional changes to their answers.  This was because
labels for these inputs were display:block and width:100%

Changing these labels to float:left clear:both should fix it.

revised no certificate state for dashboard messages and removed course message UI for future work on separate branch

This reverts commit 2b5e8a49, reversing
changes made to db0549be.

Added styles to grade out the top and bottom of the sidebar border and fixed spacing with the video and the sequence nav