The change refines and extends the documentation for the ExUnit
callbacks for test setup, "setup" and "setup_all".
* refer to the introductory Context section in function documentation
* name various ways to define setup code using atom naming unary
function, list of atoms naming unary functions and block.
* clarify that multiple setup callbacks can be used
* reduce two overly similar paragraphs about return values into a
single one
Signed-off-by: José Valim <jose.valim@plataformatec.com.br>
Florian Ebeling
77d708e1bc