(id, cb) - follow feed with key = id
(id, cb) - unfollow feed with key = id
...
(id, cb) - block feed with key = id
Note that blocking influences the observeable state of following, followers, blockers, blocking,
(id, cb) - unblock feed with key = id
(id) returns an observeable which resolves to an array of feeds that id is following
(id) returns an observeable which resolves to an array of feeds that follow id
(id) returns an observeable which resolves to an array of feeds that id is blocking
(id) returns an observeable which resolves to an array of feeds that block id