(again)

https://github.com/twbs/bootlint/wiki/W007

With the current docs directory setup, I'm making too many mistakes and have to manually address path changes and directory moves on deploy. This makes for a frustrating experience developing locally and shipping releases. With this PR, we're basically back to the same setup from v3—duplicating the dist directory into our docs directory. Not the most ideal, but very straightforward for me as the release manager.

Also, move the search code to a separate file.

Rely on `site.url` which is different for production. In that case do nothing with the search result, otherwise when in development remove our url from it.

Previously a search redirected to `https://getbootstrap.com/...`

* Update copyright range to include 2018

* Extend copyright date range on new files from 2017 to include 2018

This makes them keyboard-accessible. For mouse users, the only change
here is that the focus outline will remain on the button once clicked
(in future, this can be solved with :focus-ring, but for now this would
require a polyfill). the tooltip is explicitly hidden on `mouseleave`,
so even though the `<button>` retains focus after clicking, the tooltip
won't stay visible once mouse user moves away.
the mouse hover styles have explicitly not been make to also apply to
:focus, so as to minimise the visual impact for
mouse users (though the tooltip remains visible)
 - but due to the default outline and the custom tooltip, it
should be fairly clear when keyboard users set focus to a copy button
too.

* Fixed incorrect instruction: "Press ⌘ to copy"

It needed to be "Press ⌘C to copy"

* Updated to concatenate copy string

Updated copy command to concatenated string to prevent potential issues

* Updated the way the copy string concatenates

As per excellent suggestion by @tomlutzenberger

* Removed semicolon line endings

;P

* var not const or let

️️️ https://github.com/twbs/bootstrap/graphs/contributors

Fixes #17584
Closes #17607 by merging it

[ci skip]

Things left:
1. clear the selection after copy
2. add messages for success and error

Fixes #17196
Closes #17510

Anchor.js 1.0.0 drops the need to use anchor.css, so we remove it
from the codebase and move any leftover styles over to docs.css.

Closes #16488 by merging it.

This reverts commit 229e8889.

ZeroClipboard v2.x drops IE < 9 support.