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
This range is in conflict with [L63](#diff-feabe9f84837518430a2f3f272df2985R63) above. I believe both should be `IE<11+`: http://jsbin.com/fozixidada