Rename Autoprefixer SVGs to `*-no-whitespace`

This is as per suggested in #2. Logos can have versions with whitespace
as well as without it.
Add Autoprefixer logos with whitespace

These conform to the pseudo-standard viewBox="0 0 121.7 81.3"
Replace `autoprefixer-*-no-whitespace` logos

These have been replaced with better versions, with separate path
tags for individual paths, which allows them to be targeted.
Update README with information on Autoprefixer

Including removal of request for Autoprefixer logo
Rename Autoprefixer logos as per 4bfe7a7
Convert Autoprefixer SVGs to single path