Trait implementations should show summary line in documentation

[steveklabnik]

We've always been unsure how much information to show about implementations, and right now, we only show signatures. On HN someone suggested that including the summary line would be helpful, so that you can understand what these things actually do, if you haven't used that particular trait before.

[Manishearth]

Perhaps we should somehow link to the full description? With a [read more]-like link

[alilleybrinker]

Reducing the amount of link chasing necessary to understand what a function does sounds like a good idea, and I agree with @Manishearth that a "read more" link should be included. The question then is how much of the description to include. First sentence? Some arbitrary number of characters?