Pugjs compliance to-do list

[kylekatarnls]

• [x] dynamic mixin names
• [ ] interpolation in comments
• [x] recursive mixins
• [x] recursive interpolation
• [x] empty piped text line add whitespace

[kylekatarnls]

interpolation in comments seems a risky change and a big effort cost for few advantage. So it will be kept as known limitation.

But if someone want to do a proposition for this alignment I'm open to discussion.