Publish version with rand 0.7 dependency

[Razican]

Hello,
The current cgmath version in crates.io (0.17.0) depends on rand 0.6, but I see that the current version in the repository depends in rand 0.7 since august, which would be nice to have to avoid having projects depending on both rand 0.6 and 0.7. It's not a breaking change afaik, so it would probably be a 0.17.1 version, right?

[kvark]

Since cgmath implements the rand traits, this is a public external dependency. Updating to a breaking version therefore means a breaking version of cgmath.