Getting a user's friends

[aramperes]

Use-Case Description

Returns the profile of the user's friends. Only public profiles are returned, even if the user is authenticated (to avoid apps leaking private user info).

Semantics

Each friend object will have the same info as the "Get public profile" endpoint already available.

There will be pagination because friend lists can be quite large. See #14

Sorting will be by username, and potentially by the date the friendship was accepted (if there is such a use-case).