fixed return value is invalid
refactor use tap
refactor don't use nil? if it is not necessary
fixed Yo username allow only upper case
refactor use one line if
update help message
show error message if specified wrong parameter
add feature yo if pattern is matched
fixed can't add new Yo account
fixed always yo when posted
delete troublesome message
add show error message if no member added
refactor use method for easy to understand
refactor move to inner if statement
refactor use tap
refactor access member instead of []
fixed next instead of return in map
refactor user conditional operator instead of if
refactor use chunk and map instead of select
don't destroy every request for performance