Lint/Void should detect Kernel.tap as void-context-method

[untitaker]

Kernel.tap ignores the return value of the passed block. Rubocop should know about this.

The following code should emit a linting error, since it was clearly the programmer's intent to write a program that outputs 7:

a = 4.tap do |x|
  x = x + 3
  x
end

puts a

However, the actual behavior is that Rubocop (from master) is completely fine with that code.

I think the fix is trivial, since rubocop does analysis like this for each already. Will open a PR soon