Removed vendor prefixes, except where it fixes a specific bug or quirk

In reference to issue #558 (https://github.com/Automattic/_s/issues/558).

Some vendor prefixes remain, but only those that explicitly fix a bug or quirk on a device (there are 2 or 3 that fix bugs with the S5).
Small user base, majority of users now several versions ahead.  Version 28 isn't even listed on the referenced page any longer.