Add version & license info in .htaccess / main.css

Make it easier for people to know what version of the `.htaccess`
and `main.css` files they are using and under what license these
are provided, by adding this information within the files.

This is useful primarily when developers only copy these files from
the HTML5 Boilerplate project, forget to update their project's change
log or simply do not use anything similar to a change log.

Fix h5bp/html5-boilerplate#1424.
Update CHANGELOG

Include all changes that are not yet mentioned in the `CHANGELOG.md`.
https://github.com/h5bp/html5-boilerplate/compare/0adda79fee6ddccc46d0ba427c7e3d7277f39230...d1443410031e06421b70cd2fe39fc784c555e60a
v4.3.0
Merging upstreams Sept 10 changes