Fix code preview theme setting for comments, issues, merge requests, and snippets
User color scheme was not being used: default white color scheme was always chosen. Also, default background for code in notes was always overriding the user color scheme.
Closes#1139
See merge request !357
Also preserve code preview color scheme in events dashboard.
Assign default colors to all code blocks shown as <pre class="code highlight [color_scheme]">
Closes#1139
I decided to create a fork of rouge as rouge lacks a HTML formatter with
the required options such as wrapping a line with <span> tags.
Furthermore I was not really convinced about the clarity of rouge's
source code.
Rugments 1.0.0beta3 for now only includes some basic linting and a new
HTML formatter. Everything else should behave the same.