Whitelist three Pygments options.

- startinline
- hl_lines
- linenos
Add further testing for Highlight#sanitized_opts
Try to clarify the way sass imports happen.

/cc @mrzool
https://github.com/jekyll/jekyll-help/issues/104
Merge pull request #2642 from jekyll/pygments-opts-sanitize
Update history to reflect merge of #2642 [ci skip]
Fix spelling error. [ci skip]
Prep for v2.2.0 release.
Merge pull request #2643 from jekyll/v2-2-0-release
Always run the full test suite.
Release 2.2.0