Build: update version to 3.0.0-pre
Docs: 1.x-master branch -> compat branch; 2.x branch -> master branch
Misc: Drop support for older browsers; update support comments

That includes Opera 12.x, Firefox<29, Safari<6.0 and some hacks
for old Blackberry.

Closes gh-1820
Refs gh-1815
Misc: Remove leftover -moz-box-sizing in tests