Add deprecation messages for functions

These functions will be removed in 3.0.0+ and scripts should be updated to use
the underlying functions as noted.

* Response#http -> @robot.http
* Adapter#http -> @robot.http
* Adapter#users -> @robot.brain.users
* Adapter#userForId -> @robot.brain.userForId
* Adapter#userForName -> @robot.brain.userForName
* Adapter#userForRawFuzzyName -> @robot.brain.userForRawFuzzyName
* Adapter#userForFuzzyName -> @robot.brain.userForFuzzyName