Misc: Drop support for older browsers; update support comments

That includes IE<8, Opera 12.x, Firefox<29, Safari<6.0 and some hacks
for old Blackberry.

Fixes gh-1836
Fixes gh-1701
Refs gh-1815
Refs gh-1820
Oh, sorry, I've mixed things up, you're right.

I've confirmed it works fine in IE10 so `IE<10` it is.