[website] Make page titles follow breadcrumb scheme

[plroebuck]

Attempting to find an open webpage for this site in browser Window menu (or bookmark it) is maddening.

Examples

URL: http://unexpected.js.org/assertions/any/to-be/
Page title:

• actual: "any - to be"
• expected: "Assertions | any | to be | Unexpected.js"

URL: http://unexpected.js.org/api/addAssertion/
Page title:

• actual: "addAssertion"
• expected: "API | addAssertion | Unexpected.js"

Replacement Scheme

Page title: <top-level-menu-name> '|' [<group> '|' ]<item> '|' <site>

Benefits

1. Site can be determined from page title
2. Top-level grouping (all assertions together) in Window menu
3. User doesn't have to rename default bookmark name (which is page title)

Difficulty

Easy

[sunesimonsen]

Makes sense. The documentation page could use a lot of love ❤️

[sunesimonsen]

Will have to be changed in https://github.com/unexpectedjs/unexpected-documentation-site-generator