Merge branch 'rs-remove-user-color-scheme-class' into 'master'

Apply syntax highlighting to fenced code blocks client-side

Instead of applying the syntax highlighting scheme class to these blocks
server-side, we use Javascript and Gon to apply the user's color scheme
(or the default) client-side.

This will make it easier to cache these blocks in the future because
they're no longer state-dependent.

See merge request !1203