"mint" feature not mentioned in the doc or anywhere

[ifsheldon]

When I tried to use another crate crevice, I found the example given in its docs seems not working. The example using cgmath is here in its README. Then I found out I need to use the feature "mint" of cgmath to enable From implementations.

Although this seems not related to cgmath itself at all, I'd like to suggest you clearly mention the feature mint in your docs, because it is weird that I can turn on this feature in cargo, but I cannot find any documentation about mint feature in your docs. Maybe you have written about "mint" feature somewhere and I didn't find it. If it's so, I apologize in advance.

[aloucks]

A PR with the documentation of the mint feature would be welcomed.