This reverts commit 7220197a.

Mathjax config options added.
`compress_html` config option changed,
Mathjax script loaded by head when `page.mathjax` is truthy.
Documentation and test page added.
See also issue #198.

This reverts commit 0cfc0f03.

This reverts commit 8ac545a5.

This reverts commit c282e4b0.

This reverts commit 5d58a663.

This reverts commit 89f79138.

This reverts commit 209ac7be.

Restrict navigation to display only direct children.

This reverts commit 8ac545a5.

This reverts commit c282e4b0.

Separating new PR from #188, since indpendent.

The current default is that when a grandparent is selected, the links to its
children *and all its grandchildren* are displayed in the navigation menu.
Setting `grandchildren_branch: true` in `_config.yml` delays the display of links
to grandchildren until their parent is selected.

Automatically replaces the title with a logo

A `navigation-list-child-list` is not displayed unless the enclosing `navigation-list-item` is `active`, so it needs to be generated only when `page.url == node.url or page.parent == node.title or page.grand_parent == node.title`.

- Trimmed whitespace between html elements
  This reduced one of my files from 850KB to 115KB
- Do not sort the whole list of pages on every iteration
  This made build 3x faster