vcs: Add support for stash list.
Improve u6.GoPackageWorkingDiff to include new/untracked files.

Add pipe_util.OutputDir.
Remove old code.
github_flavored_markdown: Improve diff highlighting.

Add detailed diff highlighting, apply only for -1,+1 blocks
(GitHub-style) for now.
github_flavored_markdown: Apply detailed diff to all blocks.

Update to latest github.com/sourcegraph/syntaxhighlight API.