Remove reference to `js/css3-mediaqueries.js`

Not used in 4.6, file no longer exists.

Background:
https://github.com/textpattern/textpattern/pull/437#issuecomment-5791020
3
Merge pull request #439 from petecooper/master

Remove reference to `js/css3-mediaqueries.js`
Tidy of history text

Was adding in to GitHub, so cleaned it a bit for consistency.
Sundry changes to `README.txt`

* This is technically 4.6-dev and not 4.6.0, which might get confusing.
* Added an `About` overview.
* Pluralise `directory
* Added reference to `/js/` directory
* Switched order of post-upgrade checks, tweaked language
* Trailing slash on directory names, per the opening paragraph
Merge pull request #440 from petecooper/master

Sundry changes to `README.txt`
Optimise 80 character width
Latest build of public-side theme
Add `textpattern/update/_to_4.5.7.php` from 4.5.7 release

File was lost in transit. No changes, just a copy + paste.
Merge pull request #443 from petecooper/master

Add `textpattern/update/_to_4.5.7.php` from 4.5.7 release
Remove table alterations covered by 4.5.7 update
Tweak `setup_site_url` to include https, and uniformity

Because SSL certs have feelings, man.

Also, switch the first instance of `Textpattern` to `Textpattern CMS`
for branding.
Switch URLs to RFC2606

https://tools.ietf.org/html/rfc2606

At least one was linking to porn. Oops. The others were domain squatter
websites.
Uniformity: `admin side` to `admin-side`
Merge pull request #446 from petecooper/master

Presentational tidying and tweaks
Add missing copyright/disclaimer headers

No changes to core code, just commented entries. This adds a disclaimer
to the existing files in `textpattern/update` because they make changes
and don’t have an existing disclaimer.

Stuff in `rpc` is still credited to @kusor with appropriate author and
documentation links - again, no changes to code, just some additional
information and legal coverage.

IANAL.
Merge pull request #447 from petecooper/copyright-header-tidy

Add missing copyright/disclaimer headers
Programming style
Revert change in _to_4.0.3.php file
Tame long lineage in comments

Try to keep below 80 characters width where possible.
jQuery UI v1.11.2