Merge pull request roots#1884 from roots/beta3

Sage 9 Beta 3

Merge pull request roots#1840 from roots/8.5.1

Sage 8.5.1

Merge pull request roots#1806 from roots/beta2

Beta 2

Merge pull request roots#1795 from roots/beta1

Beta1

Merge pull request roots#1751 from roots/alpha4

Sage 9-alpha.4

Sage 8.5.0

Sage 9.0.0-alpha.2

Sage 9.0.0-alpha.1

Merge pull request roots#1621 from roots/8.4.2

Sage 8.4.2