Auto merge of rust-lang#23959 - aturon:beta-relnotes, r=alexcrichton

Collected from TWiR and the PR log.

r? @alexcrichton 
f? @brson @nikomatsakis @huonw

1.0.0-alpha.2 release

1.0.0-alpha release

0.12.0 release

0.11.0 release

0.10 release

0.9 release

0.8 release

0.7 release

0.6 release